Air bag gas generator and air bag apparatus

ABSTRACT

A gas generator for an air bag system has, in a housing provided with a gas discharge port, ignition means activated upon an impact, and gas generating means ignited and burnt by the ignition means and generate a combustion gas for inflating an air bag, and two combustion chambers storing the gas generating means. The combustion chambers are concentrically provided so as to be adjacent to each other in the radial direction of the housing, and a communicating hole which allows communication between the combustion chambers is provided, in the housing. The gas generator also has two igniters, two different gas generating means, a connector having a lead wire, a combustion chamber, ignition means provided in an inner cylindrical member, and an automatic ignition member, which can effectively restrain an occupant.

This application is a divisional of co-pending application Ser. No.09/554,740, filed on Jul. 13, 2000 and for which priority is claimedunder 35 U.S.C. § 120. Application Ser. No. 09/554,740 is the nationalphase of PCT International Application No. PCT/JP99/05295 filed on Sep.28, 1999 under 35 U.S.C. § 371. The entire contents of each of theabove-identified applications are hereby incorporated by reference. Thisapplication also claims priority of Application Nos. 10-273478;10-339934; 11-057127;.11-078306; and 11-265995 filed in Japan on Sep.28, 1998; Nov. 30, 1998; Mar. 4, 1999; Mar. 23, 1999; and Sep. 20, 1999;respectively, under 35 U.S.C. § 119.

FIELD OF THE INVENTION

The present invention relates to an air bag system which can effectivelyrestrain an occupant, and more particularly to a gas generator includingtwo or more combustion chambers, two igniters, two different gasgenerating means, an igniter having a lead wire, a combustion chamber,ignition means provided in an inner cylindrical member, and an automaticignition material.

BACKGROUND OF THE INVENTION

An air bag system, which is mounted on various kinds of vehicles and thelike including automobiles, aims to hold an occupant of the vehicle bymeans of an air bag (a bag body) . The air bag is rapidly inflated by agas when the vehicle collides at a high speed so as to prevent theoccupant from crashing into a hard object inside the vehicle, such as asteering wheel and windscreen, due to an inertia and from being injured.This kind of air bag system generally comprises a gas generator actuatedaccording to a collision of the vehicle and discharge a gas, in order tointroduce the gas into the air bag to inflate the air bag.

It is desired that the air bag system of this type can safely restrainthe occupant even when frame of the occupant (for example, whether asitting height of the occupant is long or short, whether the occupant isan adult or a child, and the like), a sitting attitude (for example, anattitude of the occupant holding the steering wheel) and the like aredifferent. Then, there has been conventionally suggested an air bagsystem which actuates by applying as small as possible impact to theoccupant at the initial stage of the actuation. Gas generators in such asystem are disclosed in JP-A 8-207696, U.S. Pat. Nos. 4,998,751, and4,950,458. JP-A 8-207696 suggests a gas generator, in which one igniterignites two kinds of gas generating agent capsules so as to generate thegas in two stages. U.S. Pat. Nos. 4,998,751 and 4,950,458 suggest a gasgenerator, in which two combustion chambers are provided for controllingactuation of the gas generator so as to generate the gas in two stagesdue to an expanded flame of the gas generating agent.

However, these gas generators have drawbacks in that an internalstructure thereof is complicated, a size of a container is large, and acost therefor becomes expensive.

Further, in JP-A 9-183359 and DE-B 19620758, there is disclosed a gasgenerator, in which two combustion chambers, each storing a gasgenerating agent, are provided in a housing and an igniter is arrangedin each combustion chamber, so as to adjust an activation timing of eachof the igniters, thereby adjusting an output of the gas generator.However, in the above gas generators, since the igniters arranged in therespective combustion chambers are independently arranged, it becomesdifficult to assemble (manufacture), the structure itself of the gasgenerator becomes complicated and a volume thereof becomes large.

SUMMARY OF THE INVENTION

In order to solve the above-problems, the present invention provides agas generator which actuates while applying as small an impact aspossible to an occupant at the initial stage of an operation and canwidely and selectively adjust an output and timing of an output increaseof the gas generator so as to safely restrain the occupant even whenframe of the occupant (for example, whether a sitting height of theoccupant is long or short, whether the occupant is an adult or a child,and the like), a sitting attitude (for example, an attitude of theoccupant holding the steering wheel) and the like are different, as wellas restricting the total size of a container, providing a simplestructure and that can be easily manufactured.

A gas generator for an air bag according to the present inventioncorresponds to a gas generator, in which two combustion chambers areprovided in a housing, and is characterized by a structure of arrangingtwo combustion chambers. In particular, it is also possible toindependently ignite and burn gas generating means accommodated in eachcombustion chamber by a different ignition means.

Namely, according to the present invention, there is provided a gasgenerator for an air bag, which includes, in the housing having a gasdischarge port or gas discharge ports, ignition means activated upon animpact, and gas generating means ignited and burnt by the ignition meansand generate a combustion gas for inflating an air bag, wherein, in thehousing, two combustion chambers for storing the gas generating meansare concentrically provided so as to be adjacent to each other in theradial direction of the housing, and a communicating hole to allowcommunication between the combustion chambers is provided.

Further, according to the present invention, there is provided a gasgenerator for an air bag, which includes ignition means activated uponan impact, and gas generating means ignited and burnt by the ignitionmeans and generate a combustion gas for inflating an air bag in ahousing formed in a cylindrical shape having an axial core length longerthan an outermost diameter, having a plurality of gas discharge ports ona peripheral wall thereof, wherein, in the housing, two combustionchambers for storing the gas generating means are concentricallyprovided so as to be adjacent to each other in the axial directionand/or the radial direction of the housing, and a communicating hole toallow communication between the combustion chambers is provided.

It is possible to provide two combustion chambers concentrically to beadjacent to each other in the axial direction and/or the radialdirection of the housing. The two combustion chambers are formed in acylindrical shape and an annular shape.

As mentioned above, by forming two combustion chambers in the housing,it is possible to make an inner structure of the gas generator simpleand independently burn the gas generating agents in the respectivecombustion chambers.

The gas generating means mentioned above is provided to inflate the airbag for restraining the occupant by the combustion gas generated by thecombustion thereof. Accordingly, when the ignition means includes atransfer charge which is ignited and burnt by the igniter to burn thegas generating means, the combustion gas generated by the combustion ofthe transfer charge is used for burning the gas generating means and isnot directly used for inflating the air bag. In this respect, both canbe definitely distinguished from each other. Further, two combustionchambers provided in the housing is exclusively used for storing the gasgenerating means. In this respect, even when the ignition means iscomposed to include the transfer charge and the transfer charge isinstalled in a defined space (hereinafter, refer to as “an accommodatingchamber”), this accommodating chamber of the transfer charge and thecombustion chamber storing the gas generating means can be definitelydistinguished from each other.

When the ignition means for igniting and burning the gas generatingmeans includes two or more igniters to be actuated upon an impact, it ispreferable that, in order to make the mounting thereof easy, theigniters are provided in a single initiator collar aligned to each otherin the axial direction. Further, when the ignition means also includesthe transfer charge which is ignited and burned in response to anactivation of the igniters, it is preferable that the transfer charge ispartitioned for each igniter, and independently ignited and burned byeach igniter, and therefore is formed such that a flame of the transfercharge for one of the igniters does not directly ignite the transfercharge in any other igniters. As this type of structure, for example, itis possible to arrange the igniters in the respectively independentigniter accommodating chambers and then arrange the transfer charges inthe igniter accommodating chambers, or to arrange the transfer chargesin a place inside the independent combustion chambers where the transfercharges can be ignited and burnt in response to the activation of theigniter.

As mentioned above, in the case of dividing the transfer charge for eachigniter, the gas generating means stored in two combustion chambers areignited and burnt by the flame generated by burning the transfer chargesarranged separately in the respective sections. That is, since thetransfer charge in each section burns in response to the activationtiming of the igniter, and the gas generating means in each combustionchamber can separately burn, an actuation performance of the gasgenerator can be optionally controlled.

Therefore, by adopting the structure of the gas generator according tothe present invention, the transfer charge partitioned for each ignitercan be independently burnt by changing the respective ignition timing ofeach igniter and accordingly, the ignition and combustion timing of thegas generating means in each combustion chamber can be staggered,therefore, the output of the gas generator can be optionally adjusted.

With respect to the two combustion chambers provided in the housing,either of the combustion chambers may be provided in the axial directionof the igniter and the other combustion chamber may be provided in theradial direction of the ignition means. Further, in the case ofcharacteristically adjusting the actuation performance of the gasgenerator, particularly a change with the passage of time in the gasdischarge amount, the two combustion chambers are charged with the gasgenerating means which are different in at least one of a burning rate,composition, composition ratio, and an amount from each other,respectively, and the respective gas generating means can beindependently ignited and burnt at an optional timing. Further, at eachcombustion chamber, the gas generating means having a different gasamount generated at a unit time may be stored.

As the gas generating means, in addition to an azide gas generatingagent based on inorganic azide which has been widely used, for example,sodium azide, non-azide gas generating agent not based on inorganicazide may be used. However, from the view of safety, non-azide gasgenerating agent is preferable, and as the non-azide gas generatingcomposition, for example, a composition containing nitrogen containingorganic compound such as tetrazole, triazole or metallic salt thereofand an oxygen containing oxidant such as alkali metal nitrate, acomposition using triaminoguanidine nitrate, carbohydroazide,nitroguanidine, and the like as fuel and nitrogen source and usingnitrate, chlorate, perchlorate or the like of an alkali metal or analkaline earth metal as an oxidant, and the like may be employed. Inaddition, the gas generating means can be suitably selected according torequirements such as a burning rate, non-toxicity, combustiontemperature, and decomposition starting temperature. In the case ofusing the gas generating means having different burning rates in therespective combustion chambers, the gas generating means having thedifferent composition or composition ratio itself may be used, suchthat, for example, the inorganic azide such as the sodium azide or thenon-azide such as the nitroguanidine is used as the fuel and thenitrogen source. Alternatively, the gas generating means obtained bychanging the shape of the composition to a pellet shape, wafer shape,hollow cylindrical shape, disc shape, single hole body shape or a porousbody shape, or the gas generating means obtained by changing a surfacearea according to the size of a formed body may be used. In particular,when the gas generating means is formed into the porous body with aplurality of through holes, an arrangement of the holes is notparticularly limited, however, in order to stabilize the performance ofthe gas generator, an arrangement structure such a distance between anouter end portion of the formed body and the center of the hole and adistance between each center of the holes are substantially equal toeach other is preferable. Concretely, in the cylindrical body having acircular cross section, for example, a preferred structure is such thatone hole is arranged at the center and six holes are formed around thehole so that the center of each hole is the apex of regular triangles ofthe equal distances between the holes. Further, in the same manner, anarrangement such that eighteen holes are formed around one hole at thecenter may be also suggested. However, the number of the holes and thearrangement structure are determined in connection with easiness ofmanufacturing the gas generating agent, manufacture cost, andperformance, and are not particularly limited.

Among the two combustion chambers mentioned above, the combustionchamber provided outside in the radial direction may contain coolantmeans for cooling the combustion gas generated due to combustion of thegas generating means on the side of a peripheral wall of the housingthereof. The coolant means is provided in the housing for the purpose ofcooling and/or purifying the combustion gas generated due to thecombustion of the gas generating means. For example, in addition to afilter for purifying the combustion gas and/or a coolant for cooling thegenerated combustion gas which have been conventionally used, a layeredwire mesh filter obtained by forming a wire mesh made of a suitablematerial into an annular layered body and compress-molding, and the likecan be used. The layered wire mesh coolant can be preferably obtained byforming a plain stitch stainless steel wire mesh in a cylindrical body,folding one end portion of the cylindrical body repeatedly and outwardlyso as to form an annular layered body and then compress-molding thelayered body in a die, or by forming a plain stitch stainless steel wiremesh in a cylindrical body, pressing the cylindrical body in the radialdirection so as to form a plate body, rolling the plate body in acylindrical shape at many times so as to form the layered body and thencompress-molding it in the die. Further, the coolant with a doublestructure with different layered wire mesh bodies at an inner side andan outer side thereof, which has a function for protecting the coolantmeans in the inner side and a function for suppressing expansion of thecoolant means in the outer side, may be used. In this case, it ispossible to restrict expansion by supporting an outer periphery of thecoolant means with an outer layer such as the layered wire mesh body,the porous cylindrical body, the annular belt body.

In the case of the gas generator, in which combustion gas generated dueto combustion of the gas generating means stored in two combustionchamber reaches the gas discharge port via a different flow paths ineach combustion chamber so that the gas generating means stored in onecombustion chamber is not directly ignited due to the combustion gasgenerated in the other combustion chambers, the gas generating means inthe combustion chambers burns in each chamber in a completelyindependent manner, and therefore, the gas generating means in eachcombustion chamber is ignited and burnt in more secure manner. As aresult, even when activation timings of two igniters are staggeredsignificantly, the flame of the gas generating means in the firstcombustion chamber, ignited by the firstly actuated igniter, does notburn the gas generating means in the other combustion chambers, so thata stable output can be obtained. This kind of gas generator can beachieved, for example, by arranging a flow passage forming member in thehousing so as to form the flow passage and introducing the combustiongas generated in the first combustion chamber to the coolant meansdirectly.

The housing, mentioned above, can be obtained by forming a diffusershell, having a gas discharge port or gas discharge ports, and a closureshell, which forms a storing space together with the diffuser shell, bycasting, forging, press-molding or the like, and joining both shells.The joining of both shells can be performed by various kinds of weldingmethods, for example, electron beam welding, laser welding, TIG arcwelding, projection welding, or the like. Forming the diffuser shell andthe closure shell by press-molding various kinds of steel plates, suchas stainless steel plate, makes manufacture easy and reducesmanufacturing cost. Further, forming both shells into a simple shape,such as a cylindrical shape, makes the press-molding of the shells easy.With respect to the material of the diffuser shell and the closureshell, stainless steel is preferable, and the material obtained byapplying nickel plating to the steel plate may be also acceptable.

In the housing mentioned above, the ignition means actuated upondetection of an impact and ignites and burns the gas generating means isfurther installed. In the gas generator according to present invention,as the ignition means, electric ignition type ignition means activatedby an electric signal (or an activating signal) transmitted from animpact sensor or the like which detects the impact is used. The electricignition type ignition means comprises an igniter activated by theelectric signal transmitted from the electric sensor which exclusivelydetects the impact by means of an electric mechanism, such as asemiconductor type acceleration sensor or the like, and a transfercharge ignited and burnt by the activation of the igniter as required.

The gas generator for the air bag mentioned above is accommodated in amodule case together with an air bag (bag body) to introduce the gasgenerated in the gas generator and inflate, so as to form the air bagapparatus. In this air bag apparatus, the gas generator is actuated whenan impact is detected by the impact sensor, and the combustion gas isdischarged from the gas discharge port in the housing. The combustiongas flows into the air bag, whereby the air bag breaks the module coverto inflate, and forms a cushion for absorbing the impact between a hardmember in the vehicle and an occupant.

The other aspects of the present invention will be described below. Theparts and combination mentioned above can be utilized in the respectiveaspects. Only features of the respective aspects will be describedbelow.

Next, a description will be given below of a gas generator including twoor more combustion chambers.

There is provided a gas generator for an air bag which can burn the gasgenerating means in each combustion chamber at a different timing and/orpower, in addition to igniting and burning the gas generating meansstored in each combustion chamber at a different timing.

Namely, according to the present invention, a gas generator for an airbag which installs, within a housing, gas discharge port, ignition meansactivated upon an impact, and gas generating means ignited and burnt bythe ignition means and generate combustion gas for inflating an air bag,is characterized in that in the housing, two or more combustion chambersfor storing the gas generating means are defined, the gas generatingmeans stored in each combustion chamber is independently ignited andburnt by the ignition means provided at each combustion chamber, and thegas generating mean stored in each combustion chamber is different fromthe ones in the other chambers in at least one of a burning rate, shape,composition, composition ratio, and amount.

The combustion chambers provided in the housing, for example, in thecase of two chambers, can be arranged such that they are concentricallyprovided so as to be adjacent to each other in the radial direction ofthe housing and a communication hole, which allows communication betweenthe combustion chambers, is provided.

As mentioned above, the gas generating means, which is different fromthe ones in the other chambers in at least one of the burning rate,shape, composition, composition ratio, and amount, are stored in aplurality of combustion chambers defined in the housing, and thereforethe actuation performance of the gas generator, in particular, thechange in the volume of the discharged gas with the passage of time canbe characteristically adjusted by independently igniting and burning thegas generating means at an optional timing. The combustion chambers arecharged by the gas generating means to provide different gas amountsgenerated at a unit time from each other, respectively. That is, in thecase of the gas generator for the air bag using the same kind of gasgenerating means for the respective combustion chambers, the actuationperformance thereof is definitely determined according to the actuationtiming of the ignition means provided in each combustion chamber.However, when the combustion chambers are charged with the gasgenerating means to provide the different combustion characteristics(for example, the burning rate, shape, composition, composition ratio,and amount) from each other, respectively, according to the presentinvention, the operation performance of the gas generator can beadjusted freely even though the actuation timings of the ignition meansare the same. Accordingly, when adjusting the actuation timing of theigniter as well as the gas generating means stored in each combustionchamber, it is possible to adjust widely and finely the operationperformance of the gas generator. In particular, in the case of changingthe shape of the gas generating means in each combustion chamber, theshape can be varied by changing a thickness or surface area of the gasgenerating agent, and in the case of changing the amount of the gasgenerating means in each combustion chamber, the weight of the gasgenerating means stored in each chamber can be different from theothers.

In the gas generator mentioned above, in the case that a plurality ofcombustion chambers are defined in the housing and charged with the gasgenerating means to provide different burning rates from each other inthe respective combustion chambers, with respect to a burning rate (Vs)of the gas generating means with a small burning rate stored in anycombustion chamber, a value (Vl/Vs) of a burning rate (Vl) of the gasgenerating means with a large burning rate stored in another combustionchamber can be adjusted to a range of between larger than 1 and smallerthan 14. For example, in the case of partitioning the housing into twochambers (that is, first and second combustion chambers) andrespectively arranging a first gas generating means and a second gasgenerating means in the first combustion chamber and the secondcombustion chamber, it is possible to adjust a burning rate of the firstgas generating means to a burning rate of the second gas generatingmeans (mm/sec) in a range of between 3:40 and 40:3.

Further, when a plurality of combustion chambers are charged with thegas generating means having different shapes from each other,respectively, the gas generating means stored in one combustion chamberand the gas generating means stored in another combustion chamber can bedifferent from each other in thickness and/or surface area thereof. Forexample, if the gas generating means having a different thickness foreach combustion chamber are used, with respect to a thickness (Ts) ofthe gas generating means with a small thickness stored in one combustionchamber, a value (Tl/Ts) of a thickness (Tl) of the gas generating meanswith a large thickness stored in another combustion chamber is adjustedin a range of between larger than 1 and not larger than 100. Moreconcretely, in the case of defining first and second combustion chambersin the housing and respectively arranging the first gas generating meansand the second gas generating means in the first combustion chamber andthe second combustion chamber, a thickness of the first gas generatingmeans to a thickness of the second gas generating means (mm) is adjustedto a range of between 0.1:10 and 10:0.1. In the porous cylindrical gasgenerating means, the thickness of the gas generating means can bemeasured by a method shown in an embodiment mentioned below.

When a plurality of combustion chambers are charged with the gasgenerating means having different surface areas per a unit weight fromeach other respectively, with respect to a surface area (Ss) of the gasgenerating means with a small surface area stored in one combustionchamber, a value (Sl/Ss) of a surface area (Sl) of the gas generatingmeans with a large surface area stored in another combustion chamber canbe suitably selected in a range of between larger than 1 and smallerthan 50.

As mentioned above, in the gas generator storing the gas generatingmeans being different in the shape and/or the amount in each of aplurality of combustion chambers, a ratio (TS1:TS2) of a total surfacearea (TS1) of the gas generating means stored in one combustion chamberto a total surface area (TS2) of the gas generating means stored inanother combustion chamber can be adjusted in a range of between 1:50and 50:1 in the case of a gas generator which is shorter in the axialdirection than in the radial direction (for example, a gas generator fora driver side), and can be adjusted to a range of between 1:300 and300:1 in the case of a gas generator which is longer in the axialdirection than the radial direction (for example, a gas generator forpassenger sides).

When changing an amount of the gas generating means in at eachcombustion chamber, a ratio (TW1:TW2) of a total weight (g) (TW1) of thegas generating means stored in one combustion chamber to a total weight(g) (TW2) of the gas generating means stored in another combustionchamber can be adjusted in a range of between 1:50 and 50:1 with a gasgenerator which is shorter in the axial direction than in the radialdirection (for example, a gas generator for a driver side), and can beadjusted to a range of between 1:300 and 300:1 with a gas generatorwhich is longer in the axial direction rather than the radial direction(for example, a gas generator for passenger sides).

In the gas generating means formed of a porous body, when usingdifferent one at each combustion chamber, it is possible to store a gasgenerating means formed in a porous cylindrical shape (for example, aseven-hole cylindrical body) in one combustion chamber and store a gasgenerating means formed in a single-hole cylindrical shape in anothercombustion chamber.

In the gas generator having the gas generating means stored in aplurality of combustion chambers, one of which is never ignited directlyby combustion gas generated in the other combustion chambers, the gasgenerating means in each combustion chamber can be completelyindependently burnt in each combustion chamber. Accordingly, in thiscase, it is possible to independently ignite and burn the gas generatingmeans stored in each combustion chamber in a more secure manner. As aresult, even in the case of significantly staggering the activationtimings of the ignition means provided in the respective combustionchambers, the flame of the gas generating means in one combustionchamber ignited by the firstly actuated ignition means does not burn thegas generating means in the rest of the combustion chambers, therefore,a stable operating output can be obtained.

Further, according to the present invention, in the gas generatormentioned above, there is provided a gas generator for an air bag,wherein two or more ignition means are disposed in the housing, and acombination of a gas discharge port formed in the housing and sealingmeans, such as a seal tape closing the gas discharge port, ischaracterized.

Namely, there is provided a gas generator for an air bag, having two ormore ignition means to be ignited upon an impact, the gas generatingmeans which is ignited and burnt by the ignition means and generatecombustion gas for inflating an air bag, and the housing with aplurality of gas discharge ports formed thereon which forms an outershell container, wherein the gas discharge ports are closed by sealingmeans for maintaining an internal pressure of the housing to apredetermined pressure, a rupturing pressure for breaking the sealingmeans is adjusted at multiple stages by controlling the gas dischargeports and/or the sealing means so as to suppress a difference of amaximum internal pressure of the housing at the time when each ignitionmeans is activated, each of the two or more combustion chambers ischarged with the gas generating means which is respectively different inat least one of a burning rate, shape, composition, composition ratio,and amount, and the gas generating means in each combustion chamber canbe independently ignited and burnt at an optional timing.

The present invention provides a gas generator for an air bagcomprising, in the housing having gas discharge ports, ignition meansactivated upon an impact and gas generating means ignited and burnt bythe ignition means and generate combustion gas for inflating the airbag, characterized in that, in the housing, two combustion chambers forstoring the gas generating means are provided concentrically so as to beadjacent to each other in the radial direction of the housing, and thecommunication hole which allows communication between the combustionchambers is provided, and the two combustion chambers are charged withthe gas generating means respectively which are different from eachother in at least one of a burning rate, shape, composition, compositionratio, and amount.

The present invention also provides a gas generator for an air bagcomprising, in the housing having a gas discharge port, ignition meansto be activated upon an impact and gas generating means ignited andburnt by the ignition means and generate a combustion gas for inflatingthe air bag, wherein, in the housing, the combustion chambers forstoring the gas generating means are defined by partitioning into two ormore chambers, and the gas generating means stored in each chamber isignited and burnt independently by the igniter provided in each chamberand then generates a different amount of a gas per a unit time from eachother in each chambers.

As mentioned above, when a plurality of combustion chambers are providedin the housing and charged with different gas generating means from eachother, respectively, the gas generating means stored in each combustionchamber is independently ignited and burnt by the different ignitionmeans at the same time or at intervals. By controlling an openingdiameter (an opening area) of the gas discharge port and/or thethickness of the seal tape for closing the gas discharge port, thepressure (hereinafter, refer to as “a combustion internal pressure”) inthe housing at the time when the gas generating means burns can beunified and the combustion performance can be stabilized. In this gasgenerator, each of two or more combustion chambers is charged with thegas generating means to provide different amounts of the generated gasat a unit time from each other respectively. The adjustment of therupturing pressure mentioned above can be performed by arranging two ormore kinds of opening diameters and/or opening areas of the gasdischarge ports. Accordingly, with respect to two kinds of openingsbeing next to each other with respect to diameters thereof among two ormore kinds of gas discharge ports formed in the housing, it ispreferable that a ratio between the large diameter gas discharge portand the small diameter gas discharge port is 4/1 to 1.1/1, and anopening area ratio is 97/3 to 3/97. Further, the adjustment of therupturing pressure is performed by arranging two or more kinds of thethickness of the sealing means. Accordingly, with respect to two kindsof sealing means being next to each other with respect to the thicknessthereof, among two or more kinds of the sealing means, it is preferablethat a ratio between them is 1.1/1 and 12/1.

Further, in the gas generator, according to the present invention, wherea plurality of combustion chambers are charged with the different gasgenerating means from each other, respectively, the gas discharge portmay be arranged to have two or more opening diameters and/or openingareas, and the sealing means may be arranged to have two of morethickness. Further, it is preferable that the sealing means is a sealtape comprising a seal layer having a thickness of 20 to 200 μm and abonding layer or an adhesive layer having a thickness of 5 to 100 μm. Inthe present invention, the seal tape means comprises a seal layer and abonding layer or a adhesive layer. In the sealing means such as the sealtape, the rupturing pressure is adjusted by the size of the gasdischarge port and/or the thickness thereof, but the maximum internalpressure in the housing at the time of combustion of the gas generatingmeans (hereinafter, refer to as “a combustion maximum internalpressure”) and the combustion performance of the gas generating meansare not adjusted.

Next, a description will be given of a gas generator including twoigniters.

According to the present invention, as one solution, there is provided agas generator for an air bag having, in the housing provided with a gasdischarge port, ignition means actuated upon an impact, and gasgenerating means ignited and burnt by the ignition means and generate acombustion gas for inflating the air bag, wherein the ignition meansincludes two or more igniters activated upon an impact and the ignitersare provided so as to be aligned to each other in an axial direction.Namely, the present invention provides a gas generator for an air bagcomprising, in the housing provided with a gas discharge port, ignitionmeans activated upon an impact, and gas generating means ignited andburnt by the ignition means and generate a combustion gas for inflatingthe air bag, wherein the ignition means has two igniters to be activatedupon the impact and the igniters are provided integrally by resin.

Further, according to the present invention, there can be provided a gasgenerator for an air bag, wherein two or more igniters contained in theignition means , as mentioned above, are installed and being fitted in asingle initiator collar so as to be aligned to each other in the axialdirection.

Still further, according to the present invention, there can be provideda gas generator for an air bag, wherein two or more igniters containedin the ignition means of the gas generator for the air bag, as mentionedabove, are structured such that the igniters are integrated by a resinso as to be aligned to each other in the axial direction.

Furthermore, according to the present invention, there can be provided agas generator for an air bag, wherein two or more igniters contained inthe ignition means of the gas generator for the air bag, as mentionedabove, are installed and being integrated by a resin in one initiatorcollar so as to be aligned to each other in the axial direction.

As mentioned above, in the air bag gas generator according to thepresent invention, since two or more igniters are provided so as to bealigned to each other in the axial direction, it is possible to draw outa lead wire for connection on the same plane in the same direction at atime of connecting the igniter to a control unit for the air bagapparatus.

Further, when two or more igniters are fitted into a single initiatorcollar and/or are integrated by a resin, a mounting operation toassemble the gas generator becomes easy.

Further, when two or more igniters are integrated by a resin in a singleinitiator collar, it is unnecessary to previously coincide an innershape of the initiator collar with the outer shape of the igniter, andit is sufficient that an inner space of the initiator collar is at leastlarger than the size of the igniter. Further, when the igniters areintegrated by the resin, a fixing member for the igniter is not requiredwithout regard to any mode of the gas generator.

According to the present invention, as an alternative solution, there isprovided a gas generator for an air bag, having, in a housing providedwith a gas discharge port, ignition means actuated upon an impact, andgas generating means ignited and burnt by the ignition means andgenerate combustion gas for inflating an air bag, wherein the ignitionmeans includes two or more igniters activated upon an impact and theigniters are integrated by a resin.

According to the present invention, as a further alternative solution,there is provided a gas generator for an air bag having, in a housingprovided with a gas discharge port, ignition means actuated upon animpact, and gas generating means ignited and burnt by the ignition meansand generate a combustion gas for inflating an air bag, wherein theignition means includes two or more igniters activated upon an impact,and the igniters are fitted into a single initiator collar.

As mentioned above, a gas generator having a simple structure and simplemanufacturing steps can be provided by fixing two or more initiators bythe igniter fixing member at the same time.

Further, according to the present invention, there can be provided a gasgenerator for an air bag in which two or more igniters contained in theignition means of the above gas generator for the air bag are integratedby a resin in a single initiator collar.

Accordingly, when two or more igniters are fixed in a single initiatorcollar by the resin, it is unnecessary to previously coincide the innershape of the initiator collar with the outer shape of the igniter, andit is sufficient that the inner space of the initiator collar is atleast larger than the size of the igniter. Further, since the ignitersare integrally fixed by the resin, a fixing member for the igniter isnot required without regard to any mode of the gas generator.

In the gas generator according to the present invention, as the ignitionmeans, an electric ignition type ignition means activated by an electricsignal (or an activating signal) transmitted from an impact sensor orthe like that detects an impact. The electric ignition type ignitionmeans comprises an igniter activated on the basis of the electric signaltransmitted from the electric type sensor which detects the impactexclusively by means of the electric mechanism such as a semiconductortype acceleration sensor, and a transfer charge ignited and burnt onactivation of the igniter.

In the gas generator for the air bag according to the present invention,the elements other than the above solutions are not particularlylimited, the same elements as those of a known gas generator for an airbag can be adopted, and any modification generally performed by thoseskilled in the art to the elements can be included.

Accordingly, the gas generator for the air bag according to the presentinvention can be structured to comprise two or more ignition means andtwo or more gas generating means (two or more combustion chambers andgas generating agents) which are independently ignited and burnt by therespective ignition means to generate a combustion gas for inflating theair bag.

Next, a description will be given of a gas generator including acombustion chamber and ignition means in an inner cylindrical member.

The gas generator for the air bag according to the present invention isa gas generator in which two combustion chambers are provided in thehousing, and is characterized by an arrangement structure of twocombustion chambers. It is possible to independently ignite and burn thegas generating means stored in the respective combustion chambers bydifferent ignition means.

Namely, according to the present invention, there is provided a gasgenerator for an air bag, having, in a housing provided with a gasdischarge port, ignition means actuated upon an impact, and gasgenerating means ignited and burnt by the ignition means and generate acombustion gas for inflating the air bag, wherein two combustionchambers storing the gas generating means are provided in the housing, acommunicating hole which allows communication between the combustionchambers is provided, one of the two combustion chambers is provided ina side of the upper space of an inner cylindrical member disposed in thehousing, the ignition means is provided in a side of the lower space ofthe inner cylindrical member, and the upper space and the lower spaceare defined by a partition wall.

Further, according to the present invention, there is provided a gasgenerator for an air bag, having, in a housing provided with a gasdischarge port, ignition means activated upon an impact, and gasgenerating means ignited and burnt by the ignition means and generate acombustion gas for inflating the air bag, wherein, in the housing, twocombustion chambers storing the gas generating means are concentricallyprovided so as to be adjacent to each other in the radial direction ofthe housing, the communicating hole which allows communication betweenthe combustion chambers is provided, an inner combustion chamber of thetwo combustion chambers is provided in a side of the upper space of aninner cylindrical member disposed in the housing, the ignition means isprovided in a side of the lower space of the inner cylindrical member,and the upper space and the lower space are defined by a partition wall.

Further, according to the present invention, there is provided a gasgenerator for an air bag having ignition means activated upon an impact,and gas generating means ignited and burnt by the ignition means andgenerate a combustion gas for inflating the air bag in a housing formedinto a cylindrical shape having an axial core length longer than anoutermost diameter, with a plurality of gas discharge ports on theperipheral wall thereof, wherein, in the housing, two combustionchambers storing the gas generating means are concentrically provided soas to be adjacent to each other in the axial direction and/or the radialdirection of the housing, the communicating hole which allowscommunication between the combustion chambers is provided, an innercombustion chamber of the two combustion chambers is provided in a sideof the upper space of an inner cylindrical member disposed in thehousing, the ignition means is provided in a side of the lower space ofthe inner cylindrical member, and the upper space and the lower spaceare defined by a partition wall.

As mentioned above, the inner structure of the gas generator can be madesimpler by arranging the inner combustion chamber and the ignition meansin upper and lower portions in the axial direction in the space formedby the defining member.

Further, as mentioned above, by concentrically arranging the twocombustion chambers in the housing, it is possible to make an innerstructure of the gas generator simple and independently burn the gasgenerating agents in the respective combustion chambers.

The gas generator for the air bag according to the present inventionincludes the gas generator having the above structure and characterizedby the arranging structure of one combustion chamber and the ignitionmeans and a method of fixing two or more ignition means.

That is, according to the present invention, in the above gas generatorfor the air bag, there can be provided a gas generator for an air bag,wherein ignition means comprises two or more igniters activated upon animpact, and each igniter is provided in an initiator collar and fixed byan igniter fixing member which covers the upper surface of the initiatorcollar. Further, there can be provided a gas generator for an air bag,wherein the two or more igniters are provided in a single initiatorcollar.

As mentioned above, by fixing two or more igniters using the igniterfixing member at once, the structure and the manufacture becomes simple.

Further, according to the present invention, in the above gas generatorfor the air bag, there can be provided a gas generator for an air bag,wherein one of the two combustion chambers is provided outside the innercylindrical member disposed in the housing, an inner space of the innercylindrical member is defined by the other combustion chamber and anignition means accommodating chamber in which the ignition meansincluding the igniters is stored, by a partitioned circular member and aseal cup member engaged with the partitioned circular member. Further,there can be provided a gas generator for an air bag, wherein thepartitioned circular member is engaged with a stepped notch portionprovided on an inner peripheral surface of the inner cylindrical member.Still further, there can be provided a gas generator for an air bag,wherein a peripheral edge of the seal cup member is bent, and the bentportion of the peripheral edge is fitted into a groove provided on theinner peripheral surface of the inner cylindrical member.

Further, according to the present invention, in the above gas generatorfor the air bag, there can be provided a gas generator for an air bag,wherein the igniter contained in the ignition means is supported by theigniter fixing member which covers the upper surface of the initiatorcollar and fixed to the initiator collar, the seal cup member has anigniter receiving port extending to the igniter fixing member, an O-ringis arranged in a space constituted by the igniter fixing member, theigniter receiving port and the igniter, and the O-ring seals between theigniter fixing member and the igniter receiving port, between theigniter fixing member and the igniter, and between the igniter receivingport and the igniter.

Further, according to the present invention, in the above gas generatorfor the air bag, there can be provided a gas generator for an air bag,wherein an O-ring is interposed between a bent portion of the peripheraledge in the seal cup portion and the inner wall surface of the innercylindrical member to which the bent portion is fitted.

As mentioned above, by using the seal cup member having a specificstructure, it is unnecessary to interpose the O-ring in the fittingportion of the seal cup and the inner cylindrical member, and therefore,the diameter of the gas generator can be smaller. Further, since it ispossible to maintain the ignition means in an airtight manner, acombustion of the transfer charge is uniformly performed in response tothe activation of the igniter, and the internal pressure is increased bythe combustion of the transfer charge, thereby expanding in the radialdirection to press the inner wall surface of the inner cylindricalmember to which the bent portion of the seal cup member is fitted, sothat an air-tightness is further improved and a combustion of thetransfer charge can be also uniformly performed.

Further, as mentioned above, by commonly using the igniter fixing memberand the seal cup member together with the O-ring, it is possible tocompletely separate two or more igniters form each other.

Next, a description will be given of the gas generator which transmitsan electric signal by a lead wire.

According to the present invention, there is provided a gas generatorfor an air bag, having ignition means actuated upon an impact, and gasgenerating means ignited and burnt by the ignition means and generate acombustion gas for inflating an air bag in a housing provided with a gasdischarge port, wherein two combustion chambers storing the gasgenerating means are provided in the housing, the communicating holewhich allows communication between the combustion chambers is provided,the ignition means comprises two or more igniters activated by anelectric signal, a lead wire for transmitting the electric signal isconnected to each igniter, and the lead wire is drawn out in the samedirection on the same plane.

As the ignition means, electric ignition type ignition means activatedby an electric signal (or an activating signal) transmitted from animpact sensor or the like for detecting the impact is used in the gasgenerator according to the present invention. The electric ignition typeignition means comprises an igniter which is actuated on the basis ofthe electric signal transmitted from the electric type sensor whichdetects an impact by an exclusively electric mechanism such as asemiconductor type acceleration sensor, and a transfer charge ignitedand burnt in response to an activation of the igniter.

Further, in two or more igniters, it is preferable that the lead wiresfor transmitting the electric signal are connected via connectors andthe connectors are arranged in parallel on the same plane.

Further, in two or more igniters, it is preferable that the lead wiresfor transmitting the electric signal are connected via the connectorsand the lead wires are drawn out by the connectors in the same directionperpendicular to the axial direction of the housing.

Further, two or more igniters are preferably provided in a singleinitiator collar and aligning in the axial direction in order tofacilitate mounting them.

Further, it is preferable that two combustion chambers storing the gasgenerating means are concentrically provided so as to be adjacent toeach other in the radial direction of the housing and a communicatinghole, which allows communication between the combustion chambers, isprovided.

Further, according to the present invention, there is provided a gasgenerator for an air bag, having ignition means activated upon animpact, and gas generating means ignited and burnt by the ignition meansand generate a combustion gas for inflating an air bag in a housing witha gas discharge port, wherein two combustion chambers storing the gasgenerating means are provided in the housing, a communicating hole whichallows communication between the combustion chambers is provided. Theignition means comprises two or more igniters activated by an electricsignal, a lead wire for transmitting the electric signal is connected toeach igniter. A lead wire extending from one of the igniters extendssubstantially on an imaginary plane perpendicular to an axial directionof the housing and a lead wire extending from another of the ignitersalso extends substantially on the same plane.

The lead wires preferably extend 90 degrees or less, and more preferably50 or 45 degrees or less with respect to one another, but can also beparalledl or extend in an opposite direction (180 degrees or less).

Further, in the gas generator for the air bag as mentioned above, therecan be provided a gas generator for an air bag having ignition meansactivated upon an impact, and gas generating means ignited and burnt bythe ignition means and generate a combustion gas, for inflating an airbag, in a housing provided with a plurality of gas discharge ports on aperipheral wall thereof and formed into a cylindrical shape having anaxial core length longer than an outermost diameter, wherein, in thehousing, two combustion chambers storing the gas generating means areconcentrically provided so as to be adjacent to each other in the axialdirection and/or the radial direction of the housing, and acommunicating hole, which allows communication between the combustionchambers, is provided.

According to the present invention, two or more lead wires can be drawnout on the same plane and in the same direction by improving themounting structure of the lead wire connected to two or more igniters,and therefore, it is possible to make an assembling process of the airbag apparatus using the gas generator for the air bag easy and also makethe structure of the apparatus simple.

Next, a description will be given of a gas generator having an automaticignition material.

A gas generator for an air bag according to the present inventioncorresponds to a gas generator having two combustion chambers in ahousing, which can completely burn gas generating means left after theactuation of the gas generator. Accordingly, no inconvenience isaffected at a time of later process, disposal or the like.

That is, according to the present invention, there is provided a gasgenerator for an air bag having ignition means activated upon an impact,and gas generating means ignited and burnt by the ignition means andgenerate a combustion gas, for inflating an air bag, in a housingprovided with a gas discharge port, wherein, in the housing, two or morecombustion chambers storing the gas generating means are defined, acommunicating hole which allows communication between the combustionchambers is provided, and an automatic ignition material (AIM) ignitedand burnt due to a transmitted heat is stored in one of the combustionchambers. For example, if the gas generating means stored in a pluralityof combustion chambers are burnt at different timing at each combustionchamber, the automatic ignition material (AIM) is preferably stored inthe combustion chamber where the gas generating means to be burnt at adelayed timing is stored. In this case, the automatic ignition material(AIM) can be ignited and burnt due to the transmission of the heatgenerated by combustion of the previously burnt gas generating agent. Itis preferable that this automatic ignition material ignites the gasgenerating agent which is to be burnt at 100 milliseconds or more afterthe ignition means for igniting the gas generating means to bepreviously burnt is activated. Further, the automatic ignition materialcan be arranged so as to be combined with the igniter contained in theignition means for igniting and burning the gas generating means to beburnt at a delayed timing (or possibly left after the actuation of thegas generator).

The gas generator which burns the gas generating means at the differenttiming at each combustion chamber can be realized, for example, byconstituting the ignition means so as to include the transfer charge tobe ignited and burnt by the activation of the igniter, dividing thetransfer charge for each igniter so as to be independently ignited andburnt at each igniter, and igniting and burning the gas generating meansstored in a plurality of combustion chambers with the flame by thecombustion of the transfer charge in the different sections.

For example, in the gas generator in which two combustion chambers forstoring the gas generating means are provided in the housing, the firstgas generating means to be firstly burnt and the second gas generatingmeans to be burnt at a later timing are arranged in each combustionchamber, and the first ignition means for igniting the first gasgenerating means and the second ignition means for igniting the secondgas generating means are further provided, the automatic ignitionmaterial (AIM) is provided in the igniter contained in the secondcombustion chamber or the second ignition means. As the automaticignition material (AIM), a material, which is ignited and burnt due to aheat generated by the combustion of the first gas generating meanstransmitted along the housing, is used.

In the case of forming two combustion chambers storing the gasgenerating means in the housing, two combustion chambers can beconcentrically provided so as to be adjacent to each other in the radialdirection of the housing and further a communication hole, which allowscommunication between the combustion chambers in the housing, can beprovided.

The automatic ignition material (AIM), which can be used in the presentinvention, adopts a material which can be ignited and burnt at least dueto a combustion heat of the (prior burning) gas generating meanstransmitted from the housing or the like (that is, a transfer heat) . Assuch a material, there is, for example, a nitrocellulose.

However, these can, of course, vary on a kind of the used gas generatingmeans, a heat transferring member which transmits the combustion heat(for example, the housing), a distance with respect to a portion wherethe firstly burning gas generating means is stored. Therefore, it isnecessary to suitably select and adopt them according to the design.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross sectional view which shows an embodiment of agas generator according to the present invention;

FIG. 2 is a back view of a gas generator according to the presentembodiment;

FIG. 3 is a partly enlarged view of a gas generator according to thepresent invention;

FIG. 4 is a vertical cross sectional view which shows another embodimentof a gas generator for an air bag according to the present invention;

FIG. 5 is a graph which shows an operating output of a gas generator foran air bag according to the present invention;

FIG. 6 is a vertical cross sectional view which shows the otherembodiment of a gas generator for an air bag according to the presentinvention;

FIG. 7 is a vertical cross sectional view which shows further the otherembodiment of a gas generator for an air bag according to the presentinvention;

FIG. 8 is a vertical cross sectional view which shows further the otherembodiment of a gas generator for an air bag according to the presentinvention;

FIG. 9 is a vertical cross sectional view which shows further the otherembodiment of a gas generator for an air bag according to the presentinvention;

FIG. 10 is an exploded perspective view of a main portion which shows apartition wall;

FIG. 11 is an exploded perspective view of a main portion which showspositioning means;

FIG. 12 is a vertical cross sectional view which shows further the otherembodiment of a gas generator for an air bag according to the presentinvention;

FIG. 13 is a vertical cross sectional view which shows further the otherembodiment of a gas generator for an air bag according to the presentinvention;

FIG. 14 is a schematic view of an air bag apparatus according to thepresent invention;

FIG. 15 is a vertical cross sectional view which shows further the otherembodiment of a gas generator according to the present invention;

FIG. 16 is a vertical cross sectional view which shows further the otherembodiment of a gas generator according to the present invention;

FIG. 17 is a vertical cross sectional view which shows further the otherembodiment of a gas generator for an air bag according to the presentinvention;

FIG. 18 is a vertical cross sectional view which shows further the otherembodiment of a gas generator for an air bag according to the presentinvention;

FIG. 19 is a vertical cross sectional view which shows further the otherembodiment of a gas generator according to the present invention;

FIG. 20 is a cross sectional view of a main portion which shows anopening portion;

FIG. 21 is a vertical cross sectional view showing an embodiment inwhich an automatic ignition material is arranged;

FIG. 22 is a schematic view which shows a method of measuring athickness in a porous cylindrical gas generating agent;

FIG. 23 is a vertical cross sectional view which shows an embodiment ofa gas generator according to the present invention;

FIG. 24 is a view for explaining a method of mounting an igniter to aninitiator collar shown in FIG. 23;

FIG. 25 is a view for explaining a method of mounting the igniter to theinitiator collar shown in FIG. 23; and

FIG. 26 is a vertical cross sectional view which shows further the otherembodiment of a gas generator for an air bag according to the presentinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

A gas generator for an air bag according to the present invention willbe described below with reference to the accompanying drawings.

Embodiment 1

FIG. 1 is a vertical cross sectional view of a gas generator accordingto a first embodiment of the present invention. FIG. 1 shows a structureparticularly suitable for a driver's side gas generator

The gas generator comprises a housing 3 formed by joining a diffusershell 1, provided with gas discharge ports, and a closure shell 2 toform an inner accommodating space. The gas generator is provided aninner cylindrical member 4 formed in a substantially cylindrical shapeand arranged in the housing 3, thereby forming a first combustionchamber 5 a outside the inner cylindrical member 4. Further, a steppednotch portion 6 is provided on an inside surface of the innercylindrical member 4, and a partition wall 7, formed in a substantiallyflat circular shape, is arranged in the stepped notch portion 6. Thepartition wall 7 further partitions an inner portion of the innercylinder into two chambers so as to form a second combustion chamber 5 bin the diffuser shell side (in the upper space side) and an ignitionmeans accommodating chamber 8 in the closure shell side (in the lowerspace side), respectively. As a result, in this gas generator, the firstcombustion chamber 5 a and the second combustion chamber 5 b areconcentrically provided in the housing 3 and arranged adjacent to eachother in the radial direction of the housing. Gas generating agents (9a, 9 b ) , burnt by ignition means activated upon an impact, forgenerating combustion gas are stored in the first and second combustionchambers. The ignition means is stored in the ignition meansaccommodating chamber 8. A through hole 10 is provided in the innercylindrical member 4 which defines the first combustion chamber 5 a andthe second combustion chamber 5 b, and the through hole 10 is closed bya seal tape 11. The seal tape 11 is ruptured when the gas generatingagent 9 b is burnt, and both combustion chambers can be communicatedwith each other by the through hole 10. This seal tape 11 needs to beadjusted on its material and a thickness so that the seal tape 11 is notruptured due to the combustion of the gas generating agent 9 a in thefirst combustion chamber 5 a, but is ruptured when the gas generatingagent 9 b in the second combustion chamber 5 b is burnt. In the presentembodiment, a stainless seal tape having a thickness of 40 μm is used.Further, the through hole 10 does not function to control an internalpressure in the combustion chamber 5 b since an opening area thereof isformed larger than a gas discharge port 26 b.

The ignition means comprises two electric ignition type igniters 12 aand 12 b activated by an activating signal outputted on a basis ofdetection by a sensor, and the igniters 12 a and 12 b are providedparallel to each other in a single initiator collar 13 while exposinghead portions thereof. As mentioned above, two igniters 12 a and 12 bare fixed to the initiator collar 13 so as to form a single member byproviding the two igniters 12 a and 12 b in the single initiator collar13, thereby facilitating an assembly to the gas generator. Inparticular, in the gas generator as illustrated in FIG. 1, since theinitiator collar 13 is formed in a size capable of being inserted intothe inner cylindrical member 4, the igniters are easily and securelyfixed by crimping the lower end of the inner cylindrical member 4 to fixthe initiator collar after inserting the initiator collar 13 providedwith two igniters 12 a and 12 b into the inner cylinder 4. Further, whenarranging two igniters (12 a, 12 b) in the initiator collar 13, thedirection of each igniter can be easily controlled. As illustrated, twoigniters are arranged eccentrically with respect to the center axis ofthe housing. In case of arranging the ignitersto align the direction ofthe igniters 12 a and 12 b, as shown in FIG. 2, lead wires 50 connectingthe igniters (12 a and 12 b) to a control unit (not shown) can be drawnout in the same direction on the same plane. In FIG. 2, the lead wires50 are connected to the igniters (12 a, 12 b) via connectors 51 a, 51 band the connectors are provided in parallel on the same plane. Byforming each connector in the shape of a L-letter, the lead wire fortransmitting an electric signal (an activating signal) to the ignitercan be provided in a direction perpendicular to the axial direction ofthe housing (that is, in the radial direction of the housing), and atthat time, the lead wire connected to each igniter can be drawn out inthe same direction.

In this embodiment, a substantially cylindrical separating cylinder 14is arranged in a space between the initiator collar 13 and the partitionwall 7 so as to surround one igniter 12 b (hereinafter, refer to as “asecond igniter”). A first transfer charge accommodating chamber 15 a isdefined in the outer side of the wall 7, and a second transfer chargeaccommodating chamber 15 b is defined in the inner side of the wall 7.The igniter and the transfer charge, constituting the ignition means ,are stored in each accommodating chambers. As a result, transfer charges(16 a, 16 b), constituting the ignition means together with theigniters, are securely partitioned into the respective igniters (12 a,12 b) . When the transfer charge 16 a in the first transfer chargeaccommodating chamber 15 a is burnt, a seal tape 18, closing theflame-transferring hole 17 provided on the cylindrical member 4, isruptured, whereby the first transfer charge accommodating chamber 15 acommunicates with the first combustion chamber 5 a. When the transfercharge 16 b in the second transfer charge accommodating chamber 15 b isburnt, a seal tape 20, closing the flame-transferring hole 19 providedon the partition wall 7, is ruptured, whereby the second transfer chargeaccommodating chamber 15 b communicates with the second combustionchamber 5 b. Accordingly, when this gas generator activates, a flamegenerated, when the first igniter 12 a is ignited (activated), ignitesand burns the transfer charge 16 a in the accommodating chamber 15 a andthen, the flame in the accommodating chamber 15 a passes through theflame-transferring hole 17 formed in the inner cylindrical member 4 andignites and burns a gas generating agent 9 a, having seven holes, storedin the first combustion chamber 5 a positioned in the radial directionof the chamber 15 a. Then, the second igniter 12 b ignites and burns thesecond transfer charge 16 b stored in the accommodating chamber 15 b andthe flame in the accommodation chamber 15 b passes through theflame-transferring hole 19, provided in the axial direction of theaccommodating chamber 15 b, and ignites and burns a gas generating agent9 b, having a single hole, stored in the second combustion chamber 5 b.The combustion gas generated in the second combustion chamber 9 b passesthrough the through hole 10, provided in the diffuser shell side 1 ofthe inner cylindrical member 4, and flows into the first combustionchamber 5 a.

Particularly, in the gas generator shown in FIG. 1, in order tostabilize an actuation performance, there is a case where the secondigniter 12 b and the first igniter 12 a are ignited simultaneously ortheigniter 12 b is not activated prior to the latter 12 a. That is, the gasgenerating agent 9 b stored in the second combustion chamber 5 b isburnt at the same time with the gas generating agent 9 a stored in thefirst combustion chamber 5 a or at timing delayed from that of thecombustion of the gas generating agent 9 a. When the gas generatingagent 9 a is burnt prior to the second gas generating agent 9 b, asmentioned above, the seal tape 11 is not ruptured by the combustion ofthe first gas generating agent 9 a, but is ruptured only by thecombustion of the second gas generating agent 9 b. Further, in the gasgenerator shown in FIG. 1, the separating cylinder 14, arranged betweenthe initiator collar 13 and the partition wall 7 is, as shown in a mainportion enlarged view in FIG. 3, arranged such that hole portions 21,corresponding to an outer shape of the separating cylinder 14, areprovided on the lower surface of the partition wall 7 and the uppersurface of the initiator collar 13, and the upper end and the lower endof the separating cylinder 14 are fitted into the respective holeportions 21. By arranging the separating cylinder 14 in this manner, aflame of the transfer charge generated in one of the transfer chargecombustion chambers does not directly burn the transfer charge in theother transfer charge accommodating chamber, and the gas generatingagents stored in two combustion chambers are respectively ignited andburnt by the flame generated by the combustion of the transfer chargesin the different chambers. Namely, in general, when the transfer chargeburns in the separating cylinder 14 (that is, in the second transfercharge accommodating chamber 15 b), a pressure of the gas generated bythe combustion serves to expand the separating cylinder in the radialdirection. However, by arranging the separating cylinder, as shown inFIG. 3, the upper and lower end portions of the separating cylinder aresecurely supported by the peripheral walls of the hole portions 21 wherethe respective portions are fitted, so that, in comparison with the caseof simply interposing the separating cylinder between the partition wall7 and the initiator collar 13, leaking of the combustion gas and theflame of the transfer charge can be prevented securely.

Further, a common coolant/filter 22 for purifying and cooling thecombustion gas generated by the combustion of the gas generating agents(9 a, 9 b) is disposed in the housing 3. An inner peripheral surface ofthe coolant/filter 22 at the diffuser shell 1 side is covered with ashort pass preventing member 23 so that the combustion gas does not passbetween an end surface of the coolant/filter 22 and a ceiling portioninner surface 28 of the diffuser shell 1. An outer layer 24 forpreventing the filter 22 from expanding outwardly due to passing of thecombustion gas or the like is arranged on the outer side thecoolant/filter 22. The outer layer 24 is, for example, formed by using alayered wire mesh body, and in addition, may be formed by using a porouscylindrical member having a plurality of through holes on a peripheralwall surface, or a belt-like suppressing layer obtained by forming abelt-like member with a predetermined width into an annular shape. A gap25 is further formed on the outer side of the outer layer 24 so that thecombustion gas can pass through the entire portion of the filter 22. Agas discharge port 26, formed in the diffuser shell 1, is closed by aseal tape 27 to stop an ambient air from entering. The seal tape 27 isruptured at a time of discharging the gas. The seal tape 27 aims toprotect the gas generating agent from a moisture in the atmosphereoutside the gas generator, and does not have any influence oncontrolling the performances such as the combustion internal pressure.

In the gas generator constituted in the above manner, when the firstigniter 12 a, disposed in the ignition means accommodating chamber 8 andin the outer side of the separating cylinder 14, is activated, thetransfer charge 16 a, stored in the first transfer charge accommodatingchamber 15 a, is ignited and burnt, and the flame thereof passes throughthe flame-transferring hole 17 in the inner cylindrical member 4 andburns the porous cylindrical first gas generating agent 9 a stored inthe first combustion chamber 5 a. When the second igniter 12 b,surrounded by the separating cylinder 14, is activated at the same timeor at a delayed timing with respect to the activation of the firstigniter 12 a, the transfer charge 16 b, stored in the second transfercharge accommodating chamber 15 b, is ignited and burnt, and the flamethereof ignites and burns the single-hole cylindrical second gasgenerating agent 9 b stored in the second combustion chamber 5 b. As aresult, the ignition timings of two igniters 12 a and 12 b are adjusted.That is, an output performance (an actuation performance) of the gasgenerator can be optionally adjusted by activating the second igniterafter the activation of the first igniter or simultaneously activatingthe first igniter and the second igniter. Therefore, under variouscircumstances, such as a speed of a vehicle and an environmentaltemperature at a time of collision, it is possible to make an inflationof the air bag in the air bag apparatus mentioned below most suitable.Particularly, in the gas generator shown FIG. 1, the respectivecombustion chambers (5 a, 5 b) are provided with gas generating agents(9 a, 9 b) having different shapes, . Namely, the porous cylindricalfirst gas generating agent 9 a is disposed in the first combustionchamber 5 a, and the single-hole cylindrical second gas generating agent9 b is disposed in the second combustion chamber 5 b. Further, theamount of the gas generating agent stored in each combustion chamber (5a, 5 b) is different. The gas generating agents 9 a is 35 g and theamount of the gas generating agent 9 b is 6 g. Consequently, in this gasgenerator, the output performance can be adjusted more precisely.Naturally, the shape, composition, composition ratio, amount, etc. ofthe gas generating agent may be changed to obtain the desired outputperformance .

The output performance of the gas generator, mentioned above, can bealso confirmed, for example, according to a tank combustion testmentioned below.

<Tank combustion test>

A gas generator for the air bag is placed in a SUS (stainless steel)tank having an inner volume of 60 liter and is connected to an electricignition circuit, provided outside the tank, after sealing the tank at aroom temperature. By setting the time to zero (o) when an ignitionelectric circuit switch is turned on (an ignition electric current isapplied), the pressure increase inside the tank is measured by apressure transducer, independently placed in the tank, for a time periodbetween 0 and 200 milliseconds. Based on the measured data, a tankpressure/time curve is generated by a computer, and a curve estimatingthe performance of the gas generator (hereinafter, refer to as “a tankcurve”) is obtained. After finishing the combustion, the gas in the tankis partly taken out and may be used for the analysis of gasses such asCO, NOx, etc.

Embodiment 2

FIG. 4 is a vertical cross sectional view which shows a secondembodiment of a gas generator for an air bag according to the presentinvention. The gas generator, shown in this drawing, is also structuredto be particularly suitable for the a driver side as in the case of thegas generator shown in FIG. 1. However, the gas generator shown in FIG.4 is different from the gas generator shown in FIG. 1, in that a flowpassage forming member 51 is arranged in the first combustion chamber 5a, and a flow passage 52, through which the combustion gas generated inthe second combustion chamber 5 b passes, is formed between the flowpassage forming member 51 and the ceiling portion of an inner surface 28of the diffuser shell 1.

The flow passage forming member 51 has an annular shape obtained bybending an inner periphery and an outer periphery of a circular memberto form an inner peripheral wall 53 and an outer peripheral wall 54. Asupporting wall 56 for forming a space with the ceiling portion of theinner surface 28 of the diffuser shell is integrally formed on acircular portion 55 connecting the both peripheral wall surfaces. Theflow passage forming member 51 is attached to the inner cylindricalmember 4 by the inner peripheral wall 53 making contact with the innercylindrical member 4, and brings a supporting wall 56 in contact withthe ceiling portion of the inner surface 28 of the diffuser shell,whereby a space is formed between the circular portion 55 and theceiling portion of the inner surface 28 of the diffuser shell. Sincemultiple through holes 57 are formed on the supporting wall 56, thespace functions as a gas flow passage 52. The gas flow passage 52 is incommunication with the second combustion chamber 5 b via the throughhole 10 provided in the inner cylindrical member 4. Therefore, thecombustion gas generated in the second combustion chamber 5 b isdischarged into the gas flow passage 52 from the through hole 10, passesthrough the coolant/filter 22 and discharged from the gas discharge port26.

In the gas generator constituted in the above manner, the firstcombustion chamber 5 a and the second combustion chamber 5 b can becommunicated with each other in the coolant/filter 22. However, thecombustion gas generated by the combustion of the gas generating agentstored in either combustion chamber passes through the coolant/filter22, and is discharged from the gas discharge port 26. Consequently, aflame generated by the gas generating agent, which is firstly ignitedand burnt, does not ignite the gas generating agent stored in the othercombustion chamber. The single-hole gas generating agent 9 a stored inthe first combustion chamber 5 a is ignited and burnt only by theactivation of the first igniter 12 a, and the gas generating agent 9 bin the second combustion chamber 5 b is ignited and burnt only by theactivation of the second igniter 12 b.

Accordingly, in the gas generator FIG. 4, even in the case ofsignificantly staggering the activation timing of two igniters 12 a and12 b, the flame of the gas generating agent ignited by the firstlyactivated igniter does not burn the gas generating agent in the othercombustion chamber, and thereby a stable tank curve can be obtained inthe tank combustion test. This becomes further advantageous particularlyin the case of activating the second igniter 12 b at a predeterminedtime after activating the first igniter 12 a. Namely, in the gasgenerator shown in FIG. 4, since the through hole 10 is not closed by aseal tape, if the flow passage forming member 51 is not used, there is apossibility that the combustion gas generated in the first combustionchamber 5 a passes through the through hole 10 of the inner cylindricalmember 4 and ignites and burns the gas generating agent 9 b in thesecond combustion chamber 5 b. However, by forming a different flowpassage foreach combustion chamber (5 a, 5 b), as in the presentembodiment, the combustion gas generated in the first combustion chamber5 a passes through the coolant/filter 22 and is discharged withoutigniting the gas generating agent 9 b in the second combustion chamber 5b. As a result, the gas generating agent 9 b, stored in the secondcombustion chamber 5 a, can be optionally ignited and burnt only byactivating the second igniter 12 a. As stated in the foregoing, in thegas generator according to the present embodiment, the through hole 10is not closed by a seal tape. But even if the hole 10 is closed by aseal tape, the gas generating agent can be further independently ignitedand burnt in each combustion chamber. Accordingly, it is possible tomake an output performance of the gas generator most suitable inaccordance with a circumstance at a time of collision of the vehicle.

Here, in the gas generator shown in FIG. 4, the transfer charge 16 b,ignited by the second igniter 12 b, is arranged in the second combustionchamber 5 b, and not in the separating cylinder 14. By arranging thetransfer charge 16 b in this manner, the flame can uniformly burn thegas generating agent 9 b in the second combustion chamber 5 b when thetransfer charge 16 b is ignited and burnt by the activation of thesecond igniter 12 b. Further , the transfer charge 16 b cannot bedirectly burnt by the flame of the transfer charge 16 a in the firsttransfer charge accommodating chamber 15 a. In FIG. 4, with respect tothe same elements as those in FIG. 1, the same reference numerals areused and a description thereof has been omitted.

Next, a description will be given of an actuation performance in thecase of performing the above tank combustion test using the gasgenerator having the structure shown in FIG. 4, by referring to FIG. 5.In this test, the gas generating agents, having different shapes, arecharged in the respective combustion chambers at different amounts. Inthe tank curve shown in FIG. 5, the gas generating agent 9 a in thefirst combustion chamber 5 a has a surface area at a unit weight of agas generating agent smaller than that of the gas generating agent 9 bin the second combustion chamber 5 b, and proportions of the chargingamount between the gas generating agents, i.e. a rate of the first gasgenerating agent to the second gas generating agent is 35/6.

In FIG. 5, “A ignition” means a tank curve obtained when only the gasgenerating agent 9 a in the first combustion chamber 5 a is burnt byactivation of the first igniter 12 a. This tank curve moves upward,drawing a gentle curve. This is because the gas generating agent 9 a inthe first combustion chamber 5 a has a surface area at a unit weight ofthe gas generating agent smaller than that of the gas generating agent 9b in the second combustion chamber 5 b, and does not burn at one timeafter ignition.

Further, “A+B (simultaneous) ignition” means a tank curve obtained whenthe first and second igniters (12 a, 12 b) are simultaneously activatedto simultaneously burn the gas generating agents (9 a, 9 b) in the firstand second combustion chambers 5 a and 5 b. In this tank curve, the tankpressure rapidly increases simultaneously when the activating signal istransmitted to both igniters (12 a, 12 b) . This is because the secondgas generating agent 9 b in the second combustion chamber 5 b having alarger surface area per a unit weight burns at a time at the same timeof the ignition to discharge the combustion gas. Thereafter, thecombustion gas is continuously generated by the gas generating agent 9 ain the first combustion chamber 5 a, so that the increased output curve(the tank curve) is maintained for a while.

Further, “A+B (T milliseconds delayed) ignition” means a tank curveobtained when the second igniter 12 b is activated to burn the gasgenerating agent 9 b in the second combustion chamber 5 b at Tmilliseconds after the first igniter 12 a to burn the first gasgenerating agent 9 a in the first combustion chamber 5 a is firstlyactivated. This tank curve is substantially the same as the tank curveof “A ignition” before T milliseconds, however, after the second igniter12 b is activated (i.e. after T milliseconds), the tank curve goesupward at a time. This is because an amount of the gas rapidly generatedby the combustion of the gas generating agent 9 b in the secondcombustion chamber 5 b is added. Here, in the tank curve of “A+B (Tmillisecond delayed) ignition”, the maximum output (X kPa) thereof ismore than the maximum output (Y kPa) of the tank curve of “A+B(simultaneous) ignition”. This is because the gas generating agents (9a, 9 b) in both the combustion chambers (5 a, 5 b) are burnt at a timein the case of “A+B (simultaneous) ignition”, however, on the otherhand, the second gas generating agent 9 b in the second combustionchamber 5 b is ignited and burnt at a T milliseconds after the first gasgenerating agent 9 b charged in the first combustion chamber 5 a, sothat the generated heat is continuously maintained at that degree.

As mentioned above, in the “A+B (T millisecond delayed) ignition” inFIG. 5, the second igniter 12 b is activated T milliseconds after thefirst igniter 12 a is activated. The delay timing can be set to anoptional interval by adjusting the ignition circuit. Accordingly, ajudging circuit judges a speed at a time of the collision of the vehicleor an attitude of an occupant (for example, a person with a sittingheight is long or short or a person with an attitude of holding to thesteering wheel), or the like at the time of the collision to set asuitable delay time and accurately activating the ignition means,whereby it is possible to inflate the air bag in an optimum inflatingmode under various circumstances.

Embodiment 3

FIG. 6 is a vertical cross sectional view which shows another embodimentof a gas generator for an air bag according to the present invention.This gas generator is structured to be particularly suitable for beingarranged in passenger side.

The gas generator shown in FIG. 6 has a cylindricalhousing 103, havingan axial core length longer than an outermost diameter and having aplurality of gas discharge ports on a peripheral wall thereof. The gasgenerator also has ignition means actuated upon an impact, gasgenerating agents (9 a, 9 b) ignited and burnt by the ignition means andgenerate a combustion gas for inflating an air bag, and a coolant/filter122 for cooling and/or purifying the combustion gas generated by thecombustion of the gas generating agents. Twocombustion chambers (105 a,105 b), provided in the housing 103, are formed into a cylindricalcombustion chamber 105 a and an annular combustion chamber 105 b,respectively, and concentrically provided so as to be adjacent to eachother with respect to an axial direction of the housing 103. Acommunicating hole 110, which allows communication between thecombustion chambers 105 a and 105 b, is provided.

The gas generator of the present embodiment is formed in a shape longerin the axial direction since the housing is formed in a long cylindricalshape in the axial direction. The gas generator formed in this shape canbe a gas generator having a simple structure and easily manufacturedwhile the output of the gas generator and the timing for increasing theoutput can be optionally adjusted by arranging two combustion chambers105 a and 105 b in a combination of the cylindrical combustion chamber105 a and the annular combustion chamber 105 b, as mentioned above,concentrically providing them so as to be adjacent to each other, andmaking both the combustion chambers communicate with each other.

The ignition means comprises two or more igniters activated upon animpact, and the respective igniters (12 a, 12 b) are provided in asingle initiator collar 113 so as to be parallel to each other. Thereby,an assembly thereof can be easily performed. Further, the igniters (12a, 12 b), fixed in the single initiator collar 113 and stored in thehousing, are arranged eccentrically with respect to an axis of thehousing.

Further, a coolant/filter 122, formed in a substantially cylindricalshape, is arranged in the housing 103 so as to oppose to a housing innerperipheral surface on which a plurality of gas discharge ports 126 areformed, and a predetermined gap 125 is obtained between the filter 122and inner periphery of the housing 103. The first combustion chamber 105a is defined adjacent to a space in which the coolant/filter 122 isinstalled, and the ignition means including two igniters (12 a, 12 b) isconcentrically arranged so as to be adjacent to the first combustionchamber 105 a. Since the annular second combustion chamber 105 b isdefined in the radial direction of the ignition means, the firstcombustion chamber 105 a and the second combustion chamber 105 b areprovided adjacent to each other in the axial direction of the housing103. The different gas generating agents (9 a, 9 b) are respectivelycharged in the first and second combustion chambers. In the gasgenerator shown in FIG. 6, a porous cylindrical first gas generatingagent 9 a and a single-hole cylindrical second gas generating agent 9 bare stored in the first combustion chamber 105 a and the secondcombustion chamber 105 b, respectively.

The above ignition means comprises transfer charges, which are ignitedand burnt according to the activation of the igniters (12 a, 12 b) andignites the gas generating agents (105 a, 105 b) by the flame thereof,and the transfer charges are partitioned for each igniter andindependently ignited and burnt by each of the igniters. A space, wherethe transfer charge partitioned for each igniter is stored, is definedby a cylindrical member, a first transfer charge accommodating chamber115 a , where a first transfer charge 116 a is stored communicates withthe first combustion chamber 105 a by a flame-transferring hole 119provided in a partition wall 107 arranged between the ignition means andthe first combustion chamber 105 a, and a second transfer chargeaccommodating chamber 115 b, where a second transfer charge 116 b isstored communicates with the second combustion chamber 105 b by aflame-transferring hole 117 formed on the cylinder member 104 whichdefines the accommodating chamber 115 b. Then, the first combustionchamber 105 a and the second combustion chamber 105 b can communicatewith each other by the through hole 110 when a seal tape 11 is ruptureddue to the combustion of the gas generating agent 9 b.

In the gas generator shown in FIG. 6, when the first igniter 12 a isactivated, the transfer charge 116 a in the first transfer chargeaccommodating chamber 115 a is ignited and burnt, and the flame thereofpasses through the flame-transferring hole 119 in the partition wallmember 107 and ignites and burns the gas generating agent 9 a stored inthe first combustion chamber 105 a to generate combustion gas. Thiscombustion gas is purified and cooled while passing through thecoolant/filter 122 and is then discharged from the gas discharge port126. On the other hand, when the second igniter 12 b is actuated, thetransfer charge 116 b in the second transfer charge accommodatingchamber 115 b is ignited and burnt, and the flame thereof ignites andburns the gas generating agent 9 b in the second combustion chamber 105b. The combustion gas generated in the second combustion chamber 105 bflows into the first combustion chamber 105 a through the through hole110 in the partition wall 107, purified and cooled while passing throughthe coolant/filter 122, and then, discharged from the gas discharge port126. The combustion gas generated by the combustion of the first gasgenerating agent and the combustion gas generated by the combustion ofthe second combustion gas are both purified and cooled while passingthrough the same coolant/filter 122. Also in the present embodiment, thegas discharge port 126 is closed by a seal tape 127. This seal tape 127,which aims to protect the gas generating agent from a moisture in theatmosphere outside the gas generator, is ruptured by the combustion gasgenerated due to the combustion of the gas generating agent so as todischarge the combustion gas. Accordingly, the seal tape 127 does notcontrol the combustion performance (the combustion internal pressure) ofthe gas generating agent. Further, the flame-transferring hole 119 andthe flame-transferring hole 117 are closed by the seal tape 20 and theseal tape 18, respectively.

Further, a communicating hole 161 for communicating both chambers isprovided in a sectioning member 160 which partitions the firstcombustion chamber 105 b and the space where the coolant/filter 122 isinstalled. The combustion gas generated in the first and secondcombustion chambers (105 a, 105 b) reaches the space containing thecoolant/filter 122 through the communicating hole 161. According to thisembodiment, the communicating hole 161 having substantially the samesize as an inner diameter of the coolant/filter 122 is formed in thesectioning member 160. Then, a wire mesh 162 is placed in thecommunicating hole 161 so that the gas generating agent 9 a in the firstcombustion chamber 105 a does not move into the space where thecoolant/filter 122 is installed, at a time of the combustion. Any kindsof wire mesh can be used for this wire mesh 162 as long as it has a meshsize that can prevent the first gas generating agent 9 a from movingduring combustion and does not have a draft resistance large enough tocontrol the combustion performance.

As mentioned above, also in the gas generator according to thisembodiment, the gas generating agents (9 a, 9 b) stored in therespective combustion chambers (105 a, 105 b) are independently ignitedand burnt by adjusting the activation timing of two igniters (12 a, 12b), so that an output performance (the actuation performance) of the gasgenerator can be optionally adjusted. Consequently, in variouscircumstances such as the speed of the vehicle at the time of collisionandan environmental temperature, it is possible to make it most suitableto inflate the air bag in the case of using an air bag apparatusmentioned below.

In relation to the embodiment shown in FIG. 6, two combustion chambersprovided in the housing can be provided so as to be adjacent to eachother in the axial direction and the radial direction of the housing, asshown in FIG. 7. Concretely, in the gas generator shown in FIG. 7, asecond combustion chamber 105 b′ is extended in the axial direction ofthe housing by bending the partition wall 107′ which defines a firstcombustion chamber 105 a′ and ignition means and a second combustionchamber 105 b′ in the axial direction, and thereafter forming a endthereof into a flange shape and placing it in contact with an innerperiphery of the housing. As a result, in the gas generator shown inFIG. 7, the second combustion chamber is extended in the axialdirection, that is, extended to the first combustion chamber side,whereby the first combustion chamber and the second combustion chamberare adjacent to each other in the axial direction and the radialdirection of the housing. Further, in this embodiment, in the case wherea peripheral wall is provided with the partition wall 107″ such that aflange shaped end of the partition wall extends to be in contact withthe sectioning member 160, as shown in FIG. 8, a first combustionchamber 105 a″ and a second combustion chamber 105 b″ are adjacent toeach other in the radial direction of the housing and concentricallyprovided. Consequently, the volume of the second combustion chamber canbe increased to a degree not less than that of the gas generator shownin FIG. 7. Particularly, since the gas generators shown in FIGS. 7 and 8can increase the volume of the second combustion chamber, they areconvenient in the case of using a lot of second gas generating agent.Further, naturally, also in the gas generators shown in FIGS. 7 and 8,in the same manner as the above gas generator shown in FIG. 6, there canbe obtained a gas generator for an air bag which can optionally adjustthe output performance (the actuation performance) of the gas generatorwhile it has a simple and compact structure. In the gas generators shownin FIGS. 7 and 8, the same reference numerals are used for the sameelements shown in FIG. 6, and a description thereof has been omitted.

Embodiment 4

FIG. 9 is a vertical cross sectional view which shows another embodimentof a gas generator for an air bag according to the present invention.The gas generator shown in this drawing is structured to be particularlysuitable for arranging in a driver side in the same manner as to that ofthe gas generator shown in FIGS. 1 and 4.

Also in the gas generator shown in this drawing, a first combustionchamber 305 a and a second combustion chamber 305 b are partitioned byan inner cylindrical member 304, and provided in the housing 3 to beconcentrically adjacent to each other. A stepped notch portion 306 isprovided in an inner peripheral surface of the inner cylindrical member304 at a predetermined height, and a partition wall 307, which definesthe second combustion chamber 305 b and an ignition means accommodatingchamber 308, is arranged in the stepped notch portion 306. In thisembodiment, the partition wall 307 is, as shown in an explodedperspective view in FIG. 10, constituted by a sectioning circular member350 engaged with the stepped notch portion 306 formed in the innercylindrical member 304 and a seal cup member 360 engaged with thesectioning circular member 350. The sectioning circular member 350 isformed in a substantially flat circular shape, and has an openingportion 351, to which a transfer charge accommodating portion 361 of aseal cup member 360 mentioned below is attached, a circular hole portion352, obtained by scraping out a bottom surface in a circular shape andstoring an upper portion of an igniter 312 b, and a secondflame-transferring hole 319, extending and pierced through asubstantially center of the circular hole portion 352. Further, the sealcup member 360 has a cylindrical transfer charge accommodating portion361 fitted into the opening portion 351 of the sectioning circularmember 350, and protrudes into the second combustion chamber 305 b, anda cylindrical igniter receiving port 362, formed at a position opposingto the circular hole portion 352 of the sectioning circular member 350and extending to a side opposite to the transfer charge accommodatingportion 361. A first transfer charge 316 a is stored inside the transfercharge accommodating portion 361, and a second igniter 312 b is inwardlyfitted to the igniter receiving port 362. The sectioning circular member350 and the seal cup member 360 are engaged with each other by fittingthe transfer charge accommodating portion 361 of the seal cup member 360into the opening portion 351 of the sectioning circular member 350, andan upper portion of the second igniter 312 b inwardly fitted to theigniter receiving port 362 exposes into the circular hole portion 352 ofthe sectioning circular member 350.

The partition wall 307, constituted by the sectioning circular member350 and the seal cup member 360, is, as shown in FIG. 9, engaged withthe stepped notch portion 306 formed on the inner peripheral surface ofthe inner cylindrical member 304. That is, the peripheral edge of thesectioning circular member 350 is supported by the stepped notch portion306, and the seal cup member 360 is supported in contact by thesectioning circular member 350. Further, the peripheral edge of the sealcup member 360 is formed by being in the same direction as that of theigniter receiving port 362, and a bent portion 363 is fitted into agroove 364 provided on the inner peripheral surface of the innercylindrical member 304. Accordingly, the sectioning circular member 350is supported by the seal cup member 360 and is prevented from moving inthe axial direction of the housing 3. Further, the partition wall 307(i.e. the seal cup member 360) and the inner cylindrical member 304 areengaged with each other with no gap by fitting the bent portion 363 inthe peripheral edge of the seal cup member 360 into the groove 364 onthe inner peripheral surface of the inner cylindrical member 304.Accordingly, in the inner cylindrical member 304, the ignition meansaccommodating chamber 308, provided in the closure shell side 2 and thesecond combustion chamber 305 b provided in the diffuser shell side 1,are securely partitioned by an ignition means sealing structurecomprising the combination of the seal cup member 360 and the groove364.

The igniter receiving port 362, formed in the seal cup member 360, isstructured such that a skirt portion thereof spreads like a fan, and anO-ring 381 is arranged in an inner side thereof, that is, between theseal cup member 360 and the second igniter 312 b stored in the storingport 362. The O-ring 381 seals the space between the receiving port 362and the second igniter 312 b. Since the O-ring 381 is also inpress-contact with an igniter fixing member 382 mentioned below, thesecond igniter 312 b is arranged in a space defined by the circular holeportion 352 of the sectioning circular member, the igniter receivingport 362 of the seal cup member, the O-ring 381, and the igniter fixingmember 382. When the seal tape 320, closing the secondflame-transferring hole 319 formed in the circular hole portion 352 ofthe sectioning circular member 350, is ruptured by the activation of thesecond igniter 312 b, the inner portion of the defined spacecommunicates with the second combustion chamber 305 b. Then, the firstigniter 312 a and the second igniter 312 b are securely separated by aseal structure comprising the skirt portion of the igniter receivingport 362, the O-ring 381, and the igniter fixing member 382(hereinafter, referred as “an igniter seal structure”). Accordingly, theflame generated by the activation of any igniter does not directly flowinto the space where the other igniter is stored.

Further, in the present embodiment, two igniters 312 a and 312 b arefixed to a single initiator collar 313 in order to secure an easinessfor arranging in the housing. Particularly, in the present embodiment,two igniters 312 a and 312 b are supported by the igniter fixing member382 engaged with the initiator collar 313, and are fixed to theinitiator collar 313. The igniter fixing member 382 is formed in a shapethat covers an upper surface of the initiator collar 313, and has a holeportion 384 passing through the upper portion of each igniter andsupporting a shoulder portion 383. Two igniters 312 a and 312 b,arranged in the initiator collar 313, are fixed to the igniter fixingmember 382 outwardly fitted to the initiator collar 313. By using theabove igniter fixing member 382, two igniters 312 a and 312 b can beeasily assembled to the initiator collar 313. In the gas generator shownin this embodiment, the first igniter 312 a and the second igniter 312 bare formed in different sizes, and the outputs thereof are different.However, igniters having the same output may be used.

In actuation of the gas generator shown in the present embodiment, theflame generated due to the activation of the first igniter 312 a ignitesand burns the first transfer charge 316 a as arranged above. The flamegenerated by the combustion of the first transfer charge 316 a neitherflows into the space where the second igniter 312 b is stored, due tothe igniter seal structure, nor flows into the second combustion chamber305 b due to the ignition means seal structure constituted by the bentportion 363 of the seal cup member 360 and the groove 364 of the innercylindrical member 304. Accordingly, the flame generated by thecombustion of the first transfer charge 316 a exclusively flows into thefirst combustion chamber 305 a through the first flame-transferring hole317 formed on the peripheral wall of the inner cylindrical member 304,and ignites and burns a first gas generating agent 309 a so as togenerate the combustion gas. The flame generated by the activation ofthe second igniter 312 b exclusively flows into the second combustionchamber 305 b through the second flame-transferring hole 319 formed onthe circular hole portion 352 of the sectioning circular member 350, andignites and burns a second gas generating agent 309 b so as to generatethe combustion gas. Particularly, in the gas generator according to thisembodiment, the second transfer charge is not arranged and the secondgas generating agent 309 a is directly ignited and burnt by the flamegenerated by the activation of the second igniter 312 b.

Then, the combustion gas generated by the combustion of the first gasgenerating agent 309 a and the second gas generating agent 309 b isthereafter purified and cooled while passing through the commoncoolant/filter 22, passes through the gap 25 and is discharged from thegas discharge port 26. The seal tapes 318 and 320 for closing the firstand second flame-transferring holes are ruptured when the flame of theigniter and the combustion gas of the transfer charge pass therethrough,and the seal tape 27 for closing the gas discharge port 26 is rupturedwhen the combustion gas passes therethrough.

As mentioned above, in the case of adjusting the ignition timing of thegas generating agents 309 a and 309 b, that is, the actuationperformance of the gas generator by staggering the activation timing ofthe respective igniters 312 a and 312 b, positioning means is formed ina portion where the igniters 312 a and 312 b are arranged, so that alead wire 15′ connected to each igniter is specified. This kind ofpositioning means can be achieved by using a different typeof connector16′ foreach igniter, for example, as shown in a main portion explodedperspective view in FIGS. 11a to 11 d. In the positioning means shown inFIG. 11a, the structure is made such that a positioning groove (orprojection) 17′ is formed in a connector and a forming position of aprojection (or groove) 18′ corresponding to the positioning groove (orprojection) 17′ is different at each igniter. Namely, the position ofthe groove (or projection) 17′ of each connector is changed so that theconnector can not be mounted regularly being interfered with each otherif the connector 16′ is not mounted in a normal direction when mountingthe connector 16′ to the gas generator. In the positioning means shownin FIG. 11b, a positioning groove (or projection) 19′ is provided onlyin one connector 21′. Namely, a connector 21A′ provided with the groove(or projection) 19′ can be engaged with an igniter 22′ in a side that aprojection (or groove) 20′ is not provided. However, a connector 21B′,provided with no groove (or projection) 19′, can not be engaged with anigniter 22 a′ in a side that the projection (or groove) 20′ is provided.As a result, an error on connecting the connector 21′ can be easilyfound at the time of assembling. In FIG. 11c, a shape of a connectingand engaging portion 23′ in each connector is different from each other.Still, in FIG. 11d, two connectors are joined to one and a positioninggroove (or projection) 24′ is further formed. As this positioning means,in addition, it is possible to suitably use means for preventing theconnectors from being erroneously connected.

Also in the gas generator shown in this embodiment, the first gasgenerating agent 309 a and the second gas generating agent 309 b areindependently ignited and burnt due to the activation of the firstigniter 312 a and the second igniter 312 b, respectively. However, thereis a case where only the first igniter 312 a is energized so as to beignited, thereby igniting and burning only the gas generating agent 309a in the first combustion chamber 305 a. Namely, this corresponds to acase where the second gas generating agent 309 b and the second igniter312 b are not burnt but remained. In this case, since an inconvenienceis caused at the time of the later process, disposal and the like, it ispreferable to burn the gas generating agent 309 b in the secondcombustion chamber 305 b at a further delayed timing (for example, 100milliseconds or more, or the like) in comparison with a normal delayedignition timing (for example, 10 to 40 milliseconds, or the like) foractivating the second igniter 312 b, after the actuation of the gasgenerator (only the first igniter 312 a). Then, as shown in FIG. 12, anautomatic igniting material 385, which is to be ignited and burnt due toa transmission of a combustion heat of the first gas generating agent309 a, can be provided in the second combustion chamber 305 b. In thiscase, the ignition of the second gas generating agent 309 b by theautomatic igniting material 385 is performed after a sufficient timemore than the normal predetermined delayed time in the case ofactivating the second igniter 312 b has passed (i.e. an interval betweenactivation of each igniter) after the activation of the first igniter312 a. That is, this is different from the matter of delaying thecombustion of the second gas generating agent 309 b (i.e., delaying theactivation of the second igniter 312 b) for the purpose of adjusting theactuation performance of the gas generator. The second gas generatingagent 309 b is not ignited and burnt by the automatic igniting agent 385while optionally delaying the activation current to the second igniter312 b to adjust the actuation performance of the gas generator. In thiscase, the automatic igniting material 385 may be arranged in combinationwith the second igniter.

The first combustion chamber 305 a and the second combustion chamber 305b are defined by the inner cylindrical member 304. A through hole 310 isprovided in this inner cylindrical member 304, and the through hole 310is closed by a stainless plate 311. The stainless plate 311 is bonded tothe inner cylindrical member 304 by an adhesive member such as anadhesive material, opens the through hole 310 exclusively by thecombustion of the second gas generating agent 309 b, but does not openby the combustion of the first gas generating agent 309 a. The throughhole 310 is closed by the stainless plate 311 in this manner because theflame of the first gas generating agent 309 a is prevented from flowinginto the second combustion chamber 305 b through the through hole 310 soas to burn the second gas generating agent 309 b. Accordingly, as longas this function can be secured, in addition to the structure of closingthe through hole by the stainless plate 311, the above can be realizedby welding, bonding or heat-sealing a rupturing plate which is to bebroken, peeled, burnt out or taken out due to a pressure generated bythe combustion of the second gas generating agent, to the innercylindrical member so as to close the through hole 310, or by providinga notch on a peripheral wall of the inner cylindrical member 304, or byforming the peripheral wall of the inner cylindrical member 304 so as topartly have a thin thickness. Further, as shown in FIG. 13, a shieldingplate 386 formed in a substantially ring shape may be arranged so as tocover the through hole 310 provided in the inner cylindrical member 304.Particularly, in the aspect of the gas generator shown in FIG. 13, theseal tape closing the through hole 310 is protected by the shieldingplate 386 even when the combustion gas is generated by the combustion ofthe first gas generating agent 309 a, and therefore, the seal tape isnot broken by the combustion of the first gas generating agent 309 a. Asmentioned above, also in the present embodiment, the through hole 310 ofthe inner cylindrical member 304 is exclusively opened only by thecombustion of the second gas generating agent 309 b but is not opened bythe combustion of the first gas generating agent 309 a. Accordingly, thecombustion gas firstly generated in the first combustion chamber 305 adoes not flow into the second combustion chamber 305 b and the gasgenerating agent 309 b in the second combustion chamber 305 b is ignitedand burnt by the activation of the second igniter 312 b (in some cases,the combustion of the automatic igniting material 385). The combustiongas generated by the combustion of the second gas generating agent 309 bpasses inside the first combustion chamber 305 a through the throughhole 310 opened by the combustion thereof, and, thereafter, is purifiedand cooled by the coolant/filter 22 so as to be discharged from the gasdischarge port 26. In FIGS. 9 to 13, the same reference numerals areused to the same elements as those in FIG. 1 and a description thereofhas been omitted.

Embodiment 5

FIG. 14 shows an embodiment of an air bag apparatus according to thepresent invention which comprises the electric ignition type ignitionmeans.

The air bag apparatus comprises a gas generator 200, an impact sensor201, a control unit 202, a module case 203, and an air bag 204. As forthe gas generator 200, the gas generator described with reference toFIG. 1 is used and the actuation performance thereof is adjusted so asto apply small an impact as possible to the occupant at the initialstage of the actuation of the gas generator.

The impact sensor 201 can be, for example, constituted by asemiconductor type acceleration sensor. This semiconductor typeacceleration sensor is structured such that four semiconductor straingauges are formed on a silicone base plate which is bent when theacceleration is applied, and these semiconductor strain gauges arebridge-connected. When the acceleration is applied, the beam defects anda strain is produced on the surface. Due to the strain, a resistance ofthe semiconductor strain gauge is changed, and the resistance change isdetected as a voltage signal in proportion to the acceleration.

The control unit 202 is provided with an ignition decision circuit, andthe signals from the semiconductor type acceleration sensor is inputtedto the ignition decision circuit. The control unit 202 startscalculation at a time when the impact signal from the sensor 201 exceedsa certain value, and when the calculated result exceeds a certain value,it outputs an activating signal to the igniter 12 of the gas generator200. The control unit 202 and the igniter 12 of the gas generator 200are connected by a lead wire taken out in the same direction on the sameplane via the connector connected to the igniter 12.

The module case 203 is formed, for example, of a polyurethane, andincludes a module cover 205. The air bag 204 and the gas generator 200are stored in the module case 203 so as to be constituted as a padmodule. This pad module is generally mounted on a steering wheel 207 inthe case of being mounted to a driver side of an automobile.

The air bag 204 is formed of a nylon (for example, a nylon 66), apolyester or the like, and a bag port 206 thereof surrounds the gasdischarge port of the gas generator and is fixed to a flange portion ofthe gas generator in a folded state.

When the semiconductor type acceleration sensor 201 detects an impact ata time of a collision of an automobile, a he signal is transmitted tothe control unit 202, and the control unit 202 starts calculation at atime when the impact signal from the sensor exceeds a certain value.When the calculated result exceeds a certain value, it outputs theactivating signal to the igniter 12 of the gas generator 200.Accordingly, the igniter 12 is activated so as to ignite the gasgenerating agent, and the gas generating agent burns and generates thegas. The gas is discharged into the air bag 204, whereby the air bagbreaks the module cover 205 to inflate, thereby forming a cushion forabsorbing an impact between the steering wheel 207 and the occupant.

A description will be given below of embodiments of a gas generatorincluding two or more combustion chambers, two igniters, two differentgas generating means, an igniter having a lead wire, a combustionchamber and ignition means in an inner cylindrical member, and anautomatic igniting material.

Embodiment 6

In the embodiment 1 mentioned above, the porous cylindrical first gasgenerating agent 9 a having seven holes may be stored in the firstcombustion chamber 5 a, and the single-hole cylindrical second gasgenerating agent 9 b may be stored in the second combustion chamber 5 b.As the single-hole cylindrical gas generating agent, for example, theagent having an inner diameter of 0.5 to 1.5 mm, preferably 0.8 mm, anouter diameter of 2 to 3 mm, preferably 2.4 mm, and a length of 2 to 6mm, preferably 4 mm is used. Further, as the seven-hole cylindrical gasgenerating agent, for example, the agent having an inner diameter of 0.6to 0.7 mm, an outer diameter of 5 to 5.3 mm, and a length of 5 mm isused. As mentioned above, by respectively storing the gas generatingagents having different shapes and different burning rates in eachcombustion chamber, it is possible to also change a generating patternof the combustion gas after the gas generating agents stored in therespective chambers start combustion. An adjustment of the generatingpattern of the combustion gas, after the respective gas generatingagents start combustion in this manner, can be additionally performed bychanging the composition and the composition ratio or the amountthereof.

As the second gas generating agent, in the gas generating agent formedin a porous cylindrical shape, a thickness thereof is specified by amethod shown in FIG. 22.

Namely, as shown in FIG. 22, in the case of forming seven through holesin the cylindrical formed body having a circular cross section, a centerof one hole among the through holes is arranged at a center of thecircle of the formed body, and the other six holes are arranged in theperiphery of the central hole. In FIG. 22, a distance (b) between thecenters of respective two holes arranged in the periphery, and adistance (c) between the center of these two holes and an outer end ofthe formed body are respectively equal to each other, and further, adistance (a) between the center of the central hole and the center ofeach holes arranged in the periphery are respectively equal to eachother. It is preferable that a regular triangle comprising (a), (b), and(a), and a regular triangle comprising (b), (c), and (c) becomesubstantially the same as each other. Six regular triangles are arrangedfrom one central hole, and a center of the peripheral six holes isarranged at an apex of the regular triangle. That is, in the gasgenerating agent mentioned above, the distance of (a)(b) and (a)corresponds to the thickness of the gas generating agent, morepreferably, it is preferable that these thickness (i.e. (a) (b) and (a))are equal to each other.

As the other embodiment of the formed body, the central hole can besurrounded by peripheral eighteen holes. The number of holes and thearranging structure can be made advantageous in the same manner asmentioned above. The number of the holes and the arranging structure canbe determined according to a cooperation between an easiness forproducing the gas generating agent, a producing cost and a performance,and is not particularly limited.

Embodiment 7

Further, in the embodiment shown in FIG. 4, the different types of gasgenerating agents are used in the first combustion chamber and thesecond combustion chamber. As mentioned above, by using the differenttypes of gas generating agent at each combustion chamber, in the samemanner as the embodiment 1, the generating pattern of the combustion gascan be changed even after the gas generating agent stored in each of thechambers starts combustion, so that a inflating pattern of the air bagcan be optionally adjusted.

Embodiment 8

In FIG. 6, even in the gas generator defining two combustion chambers inthe housing, when using the different types of gas generating agents inthe respective combustion chambers, it is possible to change thegenerating pattern of the combustion gas after the gas generating agentstored in each chamber starts burning, so that a inflating pattern ofthe air bag optionally can be adjusted.

Embodiment 9

In FIG. 9, the different types of gas generating agents are used in twocombustion chambers partitioned and formed in the housing, in the samemanner as the embodiment 1. Consequently, even after the gas generatingagent stored in each chamber starts burning, the generating pattern ofthe combustion gas can be changed and therefore, an inflating pattern ofthe air bag can be optionally adjusted.

Embodiment 10

FIG. 15 shows a vertical cross sectional view of another embodiment of agas generator for an air bag according to the present invention.

In particular, the gas generator for the air bag shown in thisembodiment is characterized by a combination of gas discharge portsformed in the housing, and sealing means, such as a seal tape, forclosing the gas discharge ports, in the gas generator shown in theembodiment 1.

The gas generator has, in a housing 3 formed by joining a diffuser shell1, provided with a gas discharge port, and a closure shell 2 which formsan inner storing space together with the diffuser shell, and an innercylindrical member 4 having a substantially cylindrical shape to definea first combustion chamber on the outer side thereof. Further, a steppednotch portion is provided inside the inner cylindrical member. Apartition wall having a substantially flat circular shape is arranged inthe stepped notch portion, and the partition wall further divides aninner portion of the inner cylinder into two chambers to form a secondcombustion chamber and an ignition means accommodating chamber 8 in thediffuser shell side and in the closure shell side, respectively. As aresult, in this gas generator, the first combustion chamber 5 a and thesecond combustion chamber 5 b are concentrically provided in the housing3 and arranged adjacent to each other in the radial direction of thehousing. Gas generating agents (9 a, 9 b), which are burnt by ignitionmeans activated upon an impact to generate combustion gas, are stored inthe first and second combustion chambers, and the ignition meansactivated upon an impact is stored in the ignition means accommodatingchamber 8.

Also in this embodiment, the different types of gas generating agentsare used in the first combustion chamber and the second combustionchamber, so that the inflating pattern of the air bag can be made mostsuitable.

A through hole 10 is provided in the inner cylindrical member 4 whichdefines the first combustion chamber 5 a and the second combustionchamber 5 b, and the through hole is closed by a seal tape 11. Since theseal tape 11 is ruptured when the gas generating agent is burnt, bothcombustion chambers can communicate with each other by the through hole10. A material and a thickness of the seal tape 11 should be adjusted sothat the seal tape is ruptured only when the gas generating agent 9 b inthe second combustion chamber 5 b is burnt. In the present embodiment, astainless seal tape having a thickness of 40 μm is used. Further, thethrough hole 10 does not have a function of controlling an internalpressure in the combustion chamber 5 b since an opening area thereof ismade larger than a gas discharge port 26 b.

The ignition means comprises two electric ignition type igniters (12 a,12 b) activated by an activating signal output on the basis of detectionby the sensor, and the igniters are provided in parallel to each otherin a single initiator collar 13 as to expose head portions thereof. Asmentioned above, two igniters become a single member by being fixed tothe initiator collar 13 by providing two igniters 12 a and 12 b in thesingle initiator collar 13, and thereby can be mounted to the gasgenerator easily. In particular, in the gas generator shown in thisembodiment, the initiator collar 13 is set to a size capable of beinginserted into the inner cylindrical member 4. Accordingly the ignitercan be easily and securely fixed by crimping a lower end of the innercylindrical member 4 to fix the initiator collar after inserting theinitiator collar 13 provided with two igniters (12 a, 12 b) into theinner cylinder 4. When arranging two igniters 12 a and 12 b in theinitiator collar 13, the direction of each igniter can be easilyrestricted.

In this embodiment, a substantially cylindrical separating cylinder 14is arranged in a space between the initiator collar 13 and the partitionwall 7 to surround one igniter 12 b (hereinafter, refer to as “a secondigniter”), a first transfer charge accommodating chamber 15 a and asecond transfer charge accommodating chamber 15 b are respectivelydefined in an outer side thereof and an inner side thereof, and theigniter and the transfer charge constituting the ignition means togetherwith the igniters are stored in the respective accommodating chambers.As a result, transfer charges 16 a and 16 b, constituting the ignitionmeans together with the igniters, are securely partitioned into therespective igniters (12 a, 12 b). A seal tape 18, closing aflame-transferring hole 17 formed in the inner cylindrical member 4, isruptured when the transfer charge 16 a stored in the first transfercharge accommodating chamber 15 a is burnt, whereby the first transfercharge accommodating chamber 15 a communicates with the first combustionchamber 5 a. Further, a seal tape 20, closing a flame-transferring hole19 formed in the partition wall 7, is ruptured when the transfer charge16 b stored in the second transfer charge accommodating chamber 15 b isburnt, whereby the second transfer charge accommodating chamber 15 bcommunicates with the second combustion chamber 5 b. Accordingly, thegas generator is actuated such that a flame, when the first igniter 12 ais ignited (activated), ignites and burns the transfer charge 16 astored in the accommodating chamber 15 a and the flame passes throughthe flame-transferring hole 17 formed in the inner cylindrical member 4,and ignites and burns a gas generating agent 9 a with seven holes storedin the first combustion chamber 5 a positioned in the radial directionof the accommodating chamber 15 a. The second igniter 12 b ignites andburns the second transfer charge 16 b stored in the accommodatingchamber l5 b and the flame thereof passes through the flame-transferringhole 19 provided in the axial direction of the accommodating chamber 15b, and ignites and burns a gas generating agent 9 b with a single holestored in the second combustion chamber 5 b disposed on an extensionthereof. The combustion gas generated in the second combustion chamber 9b passes through the through hole 10, provided in the diffuser shellside 1 of the inner cylindrical member 4, and flows into the firstcombustion chamber 5 a. Particularly, in the gas generator shown in FIG.15, the separating cylinder 14 arranged between the initiator collar andthe partition wall 7 is arranged such that a hole portion 21,corresponding to an outer shape of the separating cylinder 14, isprovided on the lower surface of the partition wall 7 and the uppersurface of the initiator collar 13, and the upper end and the lower endof the separating cylinder 14 are fitted into the respective holeportions.

By arranging the separating cylinder 14 in this manner, a flame of thetransfer charge generated in one transfer charge combustion chamber doesnot directly burn the transfer charge in the other transfer chargeaccommodating chamber, and the gas generating agents stored in twocombustion chambers are respectively ignited and burnt by the flamegenerated by the combustion of the transfer charges in the differentsections. That is, generally, when the transfer charge burns in theseparating cylinder 14 (i.e. in the second transfer charge accommodatingchamber), a pressure of the gas generated by the combustion serves toexpand the separating cylinder in the radial direction, and, byarranging the separating cylinder, the upper and lower end portions ofthe separating cylinder are securely supported by the peripheral wallsof the hole portions where the respective portions are fitted, so that,in comparison with the case of simply interposing the separatingcylinder between the partition wall and the initiator collar, leaking ofthe combustion gas and the flame of the transfer charge can be moresecurely prevented.

Further, a coolant/filter 22 for purifying and cooling the combustiongas generated by the combustion of the gas generating agents (9 a, 9 b)is arranged in the housing 3. An inner peripheral surface of thecoolant/filter 22 in the diffuser shell side 1 is covered with a shortpass prevention member 23 so that the combustion gas does not passbetween an end surface of the coolant/filter 22 and an inner surface 28of the ceiling portion of the diffuser shell 1. An outer layer 24, forsuppressing the filter 22 from outwardly expanding due to passing of thecombustion gas or the like, is arranged on the outer side of thecoolant/filter 22. The outer layer 24 is, for example, formed by alayered wire mesh body, and in addition, may be formed by a porouscylindrical member having a plurality of through holes on a peripheralwall surface or a belt-like restriction layer obtained by forming abelt-like member with a predetermined width in an annular shape. A gap25 is formed on the outer side of the outer layer 24 so that thecombustion gas can pass through the entire portion of the filter 22.

The gas generator according to the present invention is characterized bythe structure of the gas discharge port formed in the diffuser shell 1and/or the seal tape for closing this. Two kinds of gas discharge ports26 a and 26 b, having different diameters, are provided in theperipheral wall portion of the diffuser shell of the gas generator shownin FIG. 15, and the numbers of two kinds of gas discharge ports can bemade equal to each other. In this case, the diameter of the gasdischarge port 26 a is greater than the diameter of the gas dischargeport 26 b, and the numbers of the respective holes are the same andtherefore, the total opening area of the gas discharge port 26 a isgreater than that of the gas discharge port 26 b. In this embodiment,the diameter of the gas discharge port 26 a is 3.0 mm, the number ofholes thereof is 10, and the diameter of the gas discharge port 26 b is2 mm and the number of holes thereof is 6. In order to protect the gasgenerating agent from the influence of the environment such as thehumidity outside the housing, the seal tape 27 is adhered to the gasdischarge ports 26 a and 26 b from the inner peripheral surface of theperipheral wall portion of the diffuser shell 1. The seal tape 27 has awidth sufficient for simultaneously closing two kinds of gas dischargeports arranged in the axial direction of the gas generator. It ispreferable that there is 2 to 3 mm width between the upper end or thelower end of each gas discharge port 26 a and 26 b, and the upper end orthe lower end of the seal tape, and it is preferable to use the sealtape comprising an aluminum seal layer having a thickness of 20 μm to200 μm and a bonding layer having a thickness of 5 to 100 μm or anadhesive layer. However, as long as the desired effect can be obtained,the kind and structure of the seal tape are not particularly limited. Inthe present embodiment, the seal tape, having a thickness of thealuminum layer of 50 μm and a thickness of the bonding layer or theadhesive layer of 50 μm, is used. In the present embodiment, therespective gas discharge ports 26 a and 26 b are arranged in the axialdirection of the housing of the gas generator. However, in order toobtain the effect of the present invention, for example, the respectivegas discharge ports may be alternately arranged in the peripheral wallportion of the diffuser shell in a circumferential manner. Due to thecombination of the gas discharge port and the seal tape mentioned above,the pressure for breaking the seal tape is adjusted at two stages.

In this structure, at the time of actuating the gas generator, forexample, when the igniter for igniting the single-hole gas generatingagent in the combustion chamber 5 b is actuated 30 milliseconds afteractuation of the igniter for igniting the seven-hole gas generatingagent in the combustion chamber 5 a, the opening area (the diameter andthe number of the hole) of the gas discharge port 26 a is correlatedwith the combustion surface area of the gas generating agent in thecombustion chamber 5 a, and the opening area (the diameter and thenumber of the hole) of the gas discharge port 26 b is correlated withthe combustion surface area of the gas generating agent in thecombustion chamber 5 b. Conventionally, since a single diameter of gasdischarge is used, the opening area can be only correlated with thesurface area of the gas generating agent in the combustion chamber 5 aor the surface area of all the gas generating agent in the combustionchambers 5 a and 5 b. In this case, the former is an optimum conditionwhen the gas generating agent in the combustion chamber 5 a burns.However, when the gas generating agent in the combustion chamber 5 b orthe combustion chambers 5 a and 5 b continuously burns, the combustionpressure becomes too high, so that the gas generator may have anexcessive output. Further, in the latter case, when the gas generatingagent only in the combustion chamber 5 a firstly burns, the outputbecomes too gentle on the contrary, so that it is difficult to obtain asufficient restraining performance at the beginning of inflation of theair bag.

According to the present invention, since two kinds of gas dischargeports having different opening areas are provided, as shown in thepresent embodiment, to correlate with the surface area of the gasgenerating agent in each combustion chamber, it is possible to inflatethe air bag in an optimum manner regardless of the timing of theignition of the gas generating agent. In this case, there are two kindsof opening areas in the gas discharge port. However, by furtherincreasing the kinds and adjusting the rupturing pressure of the sealtape at multiple stages, the difference of the output performance due tothe environmental temperature can be suppressed.

In the gas generator constituted in the above manner, when the firstigniter 12 a arranged in the ignition means accommodating chamber 8 andoutside the separating cylinder 14 is actuated, the transfer charge 16 astored in the first transfer charge accommodating chamber 15 a isignited and burnt, and the flame passes through the frame-transferringhole 17 in the inner cylindrical member 4 and burns the porouscylindrical first gas generating agent 9 a having seven holes stored inthe first combustion chamber 5 a. When the second igniter 12 b,surrounded by the separating cylinder 14, is actuated, the transfercharge 16 b stored in the second transfer charge accommodating chamber15 b is ignited and burnt, and the flame thereof ignites and burns thesingle-hole cylindrical second gas generating agent 9 b stored in thesecond combustion chamber 5 b. Consequently, it is possible to adjustthe ignition timing of the igniters 12 a and 12 b by activating thesecond igniter after the activation of the first igniter orsimultaneously activating the first and second igniters. Therefore, anoutput performance (an actuation performance) of the gas generator canbe optionally adjusted, so that, under various kinds of circumstances,such as a speed of a vehicle and an environmental temperature at a timeof collision, an inflation of the air bag in the below air bag apparatuscan be most suitable. Particularly, in the gas generator shown in thisembodiment, the gas generating agents (9 a, 9 b) having different shapesare used for the respective combustion chambers (5 a, 5 b), and theporous cylindrical first gas generating agent 9 a and the single-holecylindrical second gas generating agent 9 b are respectively stored inthe first combustion chamber 5 a and the second combustion chamber 5 b.Further, the amount of the gas generating agent stored in eachcombustion chamber (5 a, 5 b) is different, and the gas generatingagents 9 a and 9 b at an amount of 35 g and 6 g are respectively storedin the first combustion chamber 5 a and the second combustion chamber 5b. As a result, in this gas generator, the output performance can bemore precisely adjusted. It is, of course, possible to suitably changethe shape, composition, composition ratio, amount, and the like of thegas generating agent for obtaining a desired output performance.

According to the present invention, due to the use combination of two ormore igniters and two or more kinds of gas discharge ports as mentionedabove, the internal pressure at a time of operating the gas generatorcan be equalized and the combustion performance can be stabilized.

A gas generator shown in FIG. 16 has the same structure as that shown inFIG. 15 except for the structure of the gas discharge port provided inthe diffuser shell of the housing and the seal tape closing it. The samereference numerals are used for the same elements as those shown in FIG.15, and a description thereof has been omitted. FIG. 16 corresponds toan embodiment structured such that the opening area (the diameter andthe number of the holes) of the respective gas discharge port is thesame. However, the thickness of the seal tape is changed, in order toadjust the rupturing pressure of the seal tape at two stages. In thiscase, the gas discharge port 26 a and the gas discharge port 26 b arevertically arranged in the axial direction of the housing, and thethickness of the seal tape 27 b for closing the gas discharge port 26 bis made thicker than the thickness of the seal tape 27 a for closing thegas discharge port 26 a. However, the thickness of the seal tape isrestricted for adjusting the output performance (the operatingperformance) of the gas generator, and the internal pressure of thehousing, at the time of burning the gas generating agent, is adjusted bythe opening area of the gas discharge port. Namely, the seal tape doesnot influence the maximum combustion internal pressure. The openingareas (the diameters and the numbers of the holes) of the gas dischargeports 26 a and 26 b are all the same. In this case, for example, theopening area of the gas discharge port 26 a and the thickness of theseal tape 27 a are adjusted so that the seal tape 27 a for closing thegas discharge port 26 a is all ruptured when the gas generating agent 9a in the combustion chamber 5 a is burnt. When the gas generating agent9 b in the combustion chamber 5 b subsequently burns, or when the gasgenerating agents 9 a and 9 b in the combustion chambers 5 a and 5 bsimultaneously burn, a higher combustion internal pressure is generated.In this case, the thicker seal tape 27 b is adhered to the gas dischargeport 26 b so that the seal tapes 27 a and 27 b for covering all the gasdischarge ports 26 a and 26 b are ruptured. That is, since the seal tape27 a on the gas discharge port 26 a is adjusted to a thickness which isruptured by the combustion of the gas generating agent 9 a in thecombustion chamber 5 a, the seal tape 27 b on the gas discharge port 26b does not need to be ruptured. Accordingly, since the surface area ofthe gas generating agent in the combustion chamber 5 a is correlatedwith the opening area only of the gas discharge port 26 a, the gasgenerating agent provides an optimum combustion. Further, thereafter,when the gas generating agent 9 b in the combustion chamber 5 b burns ata delayed timing, or when the gas generating agents 9 a and 9 b in bothof the combustion chambers simultaneously burn, a higher combustionpressure is generated, so that even the seal tape 27 b on the gasdischarge port 26 b can be ruptured, and an increase of the internalpressure can be restricted, and then, optimally inflation of the air bagwithout regard to the ignition timing is realized. Also in this case, asmentioned with respect to FIG. 15, a material and a structure of theseal tape, the way of arranging the gas discharge port, etc. do notcorrespond to a limiting element for obtaining the aimed effect, but anoptional specification can be adopted. Additionally, by changing thethickness at multiple stages, a gas generator, less influenced by theenvironmental temperature, etc., can be obtained in the same manner.

In the two embodiments shown in FIGS. 15 and 16, only the opening areaof the gas discharge port or only the thickness of the seal tape ismodified in some way. However, it is possible to modify both of them.

Embodiment 11

FIG. 17 shows a vertical cross sectional view of another embodiment of agas generator for an air bag according to the present invention. The gasgenerator is structured such as to be particularly suitable for beingarranged in a passenger side of a vehicle

The gas generator shown in this embodiment has, in a housing 103,provided with a plurality of gas discharge ports on a peripheral wallthereof, in a cylindrical shape having an axial core length longer thanan outermost diameter, ignition means activated upon an impact, gasgenerating agents (9 a, 9 b) ignited and burnt by the ignition means andgenerate a combustion gas for inflating the air bag, and acoolant/filter 122 for cooling and/or purifying the combustion gasgenerated by the combustion of the gas generating agents. Two combustionchambers (105 a, 105 b) are concentrically provided in the housing 103so as to be adjacent to each other in the axial direction of the housing103, and a communicating hole 110, which allows communication betweenthe combustion chambers 105 a and 105 b, is provided.

The gas generator, shown in the present embodiment, has a long shape inthe axial direction since the housing is formed into a long cylindricalshape in the axial direction. In the gas generator formed into thisshape, there can be provided a gas generator having a simple structureand easily manufactured while the output of the gas generator and thetiming for increasing the output can be optionally adjusted byconcentrically providing two combustion chambers 105 a and 105 b so asto be adjacent to each other and making both the combustion chamberscommunicate with each other.

Since the ignition means comprises two or more igniters activated uponan impact and the respective igniters (12 a, 12 b) are provided in oneinitiator collar 113 so as to be parallel to each other, an assemblythereof becomes easy .

Further, in the housing 103, a coolant/filter 122, formed in asubstantially cylindrical shape, is arranged so as to oppose the innerperipheral surface of the housing on which a plurality of gas dischargeports 126 a and 126 b are formed, and a predetermined gap 125 is securedbetween the filter 122 and the inner periphery of the housing. The firstcombustion chamber 105 a is defined so as to be adjacent to a spacewhere the coolant/filter 122 is stored, and the ignition meanscomprising two igniters (12 a, 12 b) is concentrically arranged so as tobe adjacent to the first combustion chamber 105 a. Further, the annularsecond combustion chamber 105 b is defined in the radial direction ofthe ignition means, and therefore, the first combustion chamber 105 aand the second combustion chamber 105 b are provided so as to beadjacent to each other in the axial direction of the housing 103. Thedifferent gas generating agents (9 a, 9 b) are respectively charged inthe first and second combustion chambers, and in the gas generator ofthis embodiment , the porous cylindrical first gas generating agent 9 aand the single-hole cylindrical second gas generating agent 9 b arerespectively stored in the first combustion chamber 105 a and the secondcombustion chamber 105 b. Accordingly, the operating performance of thegas generator can be made most suitable.

The above ignition means comprises a transfer charge ignited and burntby activation of igniters (12 a, 12 b) and ignites the gas generatingagents (105 a, 105 b) by the flame thereof, and the transfer charge ispartitioned for each igniter and is independently ignited and burnt byeach igniter. A space, where the transfer charge of each igniter isstored, is defined by a cylindrical member, a first transfer chargeaccommodating chamber 115 a, where a first transfer charge 116 a isstored, is communicated with the first combustion chamber 105 a by aflame-transferring hole 119 on a partition wall 107 arranged between theignition means and the first combustion chamber 105 a, and a secondtransfer charge accommodating chamber 115 b, where a second transfercharge 116 b is stored, is communicated with the second combustionchamber 105 b by a flame-transferring hole 117 formed on the cylindermember 104 which defines the accommodating chamber 115 b. The firstcombustion chamber 105 a and the second combustion chamber 105 b arecommunicated with each other by the through hole 110 formed on thepartition wall 107.

In the gas generator of this embodiment, when the first igniter 12 a isactivated, the transfer charge 116 a in the first transfer chargeaccommodating chamber 115 a is ignited and burnt, and the flame thereofpasses through the flame-transferring hole 119 in the partition wallmember 107 and ignites and burns the gas generating agent 9 a, arrangedin the first combustion chamber 105 a, so as to generate the combustiongas. The combustion gas is purified and cooled while passing through thecoolant/filter 122 and is discharged from a gas discharge port. On theother hand, when the second igniter 12 b is activated, the transfercharge 116 b in the second transfer charge accommodating chamber 115 bis ignited and burnt, and the flame thereof ignites and burns the gasgenerating agent 9 b in the second combustion chamber 105 b. Thecombustion gas generated in the second combustion chamber 105 b passesinside the first combustion chamber 105 a through the through hole 110of the partition wall 107, is purified and cooled while passing throughthe coolant/filter 122 and is discharged from the gas discharge port.Further, also in the gas generator of this embodiment, the through hole110 communicating the first combustion chamber with the secondcombustion chamber is closed by a seal tape 111 which is exclusivelyruptured by the combustion of the gas generating agent in the secondcombustion chamber. Besides, also in the present embodiment, in the samemanner as the gas generator in FIG. 14, the gas discharge portscomprises a large diameter gas discharge port 126 a and a small diametergas discharge port 126 b, and these ports are closed by a seal tape 127.Namely, in the embodiment shown in FIG. 16, it is possible to controlthe rupturing pressure of the seal tape by making the thickness of theseal tape constant and setting the opening area of the gas dischargeport to two kinds as shown in FIG. 14, and thereby the optimum outputcan be always adjusted most suitably regardless of the combustion timingof the combustion chambers 105 a and 105 b and the gas generating agents9 a and 9 b. The gas discharge port is disposed in the peripheral wallportion of the cylindrical housing, and the surface area of the gasgenerating agent 9 a in the combustion chamber 105 a is correlated withthe gas discharge port 126 a, and the surface area of gas generatingagent 9 b in the combustion chamber 105 b is correlated with the openingarea of the gas discharge port 126 b. Since the actuation principle isthe same as that of FIG. 15, a detailed description has been omitted.

Further, a communicating hole 161, communicating both chambers, isprovided in a sectioning member 160, which defines the first combustionchamber 105 a and the space where the coolant/filter 122 is stored. Thecombustion gas generated in the first and second combustion chambers(105 a, 105 b) reaches the storing space for the coolant/filter 122through the communicating hole 161. According to this embodiment, acommunicating hole 161, having substantially the same size as an innerdiameter of the coolant/filter 122, is formed in the sectioning member160. Then, a wire mesh 162 is placed in the communicating hole 161 sothat the gas generating agent 9 a in the first combustion chamber 105 adoes not move to a side of the space where the coolant/filter 122 isstored, at the combustion. Any kind of wire mesh can be used as thiswire mesh 162 as long as it has a mesh size sufficient to preventmovement of the first gas generating agent 9 a during the combustion,but does not have a draft resistance large enough to control thecombustion performance.

As mentioned above, also in the gas generator according to thisembodiment, the gas generating agents (9 a, 9 b), stored in therespective combustion chambers (105 a, 105 b), are independently ignitedand burnt by adjusting the activation timing of two igniters (12 a, 12b), so that the output performance (the actuation performance) of thegas generator can be optionally adjusted. As a result, in variouscircumstances such as the speed of the vehicle at a time of collision,an environmental temperature, and the like, it is possible to make itmost suitable to inflate the air bag in case of an air bag apparatusmentioned below.

In FIG. 17, two combustion chambers, provided in the housing, areprovided to be adjacent to each other in the axial direction and theradial direction of the housing. Concretely, in the gas generator shownin FIG. 17, a second combustion chamber 105 b is extended in the axialdirection of the housing by bending a first combustion chamber 105 a anda partition wall 107 which defines ignition means and a secondcombustion chamber 105 b in the axial direction, thereafter forming anend thereof into a flange shape and placing it in contact with an innerperiphery of the housing. As a result, in the gas generator shown inFIG. 17, the second combustion chamber is extended in the axialdirection, that is, extended to a side of the first combustion chamber,whereby the first combustion chamber and the second combustion chamberare adjacent to each other in the axial direction and the radialdirection of the housing. Since the gas generators, shown in FIG. 17,can increase the volume of the second combustion chamber, they areconvenient in the case of using a lot of second gas generating agents.

FIG. 18 is a cross sectional view of a gas generator, which mainlyrestrains an occupant sitting in a passenger side of a vehicle in thesame manner as that shown in FIG. 17, and shows an embodiment structuredsuch as to make the opening area in each of the gas discharge portsconstant, as shown in FIG. 16, but changing the thickness of the sealtape to adjust the rupturing pressure. Namely, the gas discharge port126 a and the gas discharge port 126 b are vertically arranged in theaxial direction of the housing, and with respect to the thickness of theseal tape 127 a for closing the gas discharge port 126 a, the thicknessof the seal tape 127 b for closing the gas discharge port 126 b is madelarger. The opening areas (the diameters and the numbers of the holes)of the gas discharge ports 126 a and 126 b are the same. In theactuation of the gas generator shown in FIG. 18, the same referencenumerals are used as the same elements as those shown in FIG. 3, and adescription thereof has been omitted. Since the structure and theoperation of the gas discharge port and the seal tape are the same asFIG. 16, the description of the operation thereof will has been omitted.

In the case of the gas generator for restraining the occupant sitting ina passenger side of a vehicle, as shown in FIGS. 17 and 18, in the samemanner, it is possible to perform more particular adjustments to avoidbeing influenced by the ambient temperature and the like by furtherincreasing the kind of the opening of the gas discharge port and furtherincreasing the kind of the thickness of the seal tape. Naturally, theopening area in the discharge port and the thickness of the seal tapemay be simultaneously combined.

Embodiment 12

FIG. 19 is a vertical cross sectional view of a gas generator for an airbag according to another embodiment of the present invention. The gasgenerator shown in this embodiment also has a structure particularlysuitable for a driver side of a vehicle in the same manner as that ofthe gas generator shown in FIGS. 15 and 16.

The gas generator shown in FIG. 19 has the same structure as that shownin FIG. 15 except for the structure of the partition wall whichpartitions the inner portion of the inner cylindrical member into thesecond combustion chamber and the ignition means accommodating chamber,and accordingly, the same reference numerals are used for the sameelements as those in FIG. 15 and a description thereof has been omitted.

Particularly, the gas generator shown in this embodiment is structuredsuch that a substantially flat circular partition wall 307, whichdefines the inner side of the inner cylindrical member into the secondcombustion chamber, and the ignition means accommodating chambercomprises, as shown in an exploded perspective view in FIG. 2 mentionedabove, a sectioning circular member 350 engaged with the stepped notchportion 306 of the inner cylindrical member 304 and a seal cup member360 engaged with the sectioning circular member 350.

The partition wall 307, comprising the sectioning circular member 350and the seal cup member 360, are, as shown in FIG. 19, engaged with thestepped notch portion 306 formed on the inner peripheral surface of theinner cylindrical member 304. That is, the peripheral edge of thesectioning circular member 350 is supported by the stepped notch portion306, and the seal cup member 360 is supported in contact with thesectioning circular member 350. Further, the peripheral edge of the sealcup member 360 is formed by being bent in the same direction as that ofthe igniter receiving port 362, and the bent portion 363 is fitted intoa groove 364 provided on the inner peripheral surface of the innercylindrical member 304. Accordingly, the sectioning circular member 350is supported by the seal cup member 360 and is prevented from moving inthe axial direction of the housing 3. Further, the partition wall 307(i.e. the seal cup member 360) and the inner cylindrical member 304 areengaged with each other without a gap by fitting the bent portion 363 inthe peripheral edge of the seal cup member 360 into the groove 364 onthe inner peripheral surface of the inner cylindrical member 304.Consequently, in the inner cylindrical member 304, the ignition meansaccommodating chamber 308, provided in the closure shell side 2 and thesecond combustion chamber 305 b provided in the diffuser shell side 1,are securely partitioned by an ignition means sealing structurecomprising a combination of the seal cup member 360 and the groove 364.

The igniter receiving port 362 formed in the seal cup member 360 isstructured such that a skirt portion thereof spreads like a fan, and anO-ring 381 is arranged in an inner side thereof, that is, between thisand the second igniter 312 b stored in the storing port 362, and sealingbetween the storing port 362 and the second igniter 312 b is performed.Since the O-ring 381 is also press-contacted to an igniter fixing member382 which fixes two igniters (312 a, 312 b) to a single initiator collar313, the second igniter 312 b is arranged in a space defined by thecircular hole portion 352 of the sectioning circular member, the igniterreceiving port 362 of the seal cup member, the O-ring 381, and theigniter fixing member 382. When the seal tape 320, closing the secondflame-transferring hole 319 formed in the circular hole portion 352 ofthe sectioning circular member 350, is ruptured by activation of thesecond igniter 312 b, the inner portion of the defined spacecommunicates with the second combustion chamber 305 b. The first igniter312 a and the second igniter 312 b are securely separated by a sealstructure comprising the skirt portion of the igniter receiving port362, the O-ring 381, and the igniter fixing member 382 (hereinafter,refer to as “an igniter seal structure”). Accordingly, the flamegenerated by the activation of one igniter does not directly flow intothe space where the other igniter is stored. The igniter fixing member382 is formed in a shape which covers the upper surface of the initiatorcollar 313, and has a hole portion 384 passing through the upper portionof each igniter and supporting a shoulder portion 383. Two igniters 312a and 312 b, arranged in the initiator collar 313, are fixed to theigniter fixing member 382 outwardly fitted to the initiator collar 313.By using the above igniter fixing member 382, two igniters 312 a and 312b are easily assembled to the initiator collar 313. Besides, in the gasgenerator shown in this embodiment, the first igniter 312 a and thesecond igniter 312 b are formed in different sizes and have thedifferent outputs. However, the igniters having the same output may beused.

Also in the gas generator shown in this embodiment, in the same manneras the gas generator shown in FIG. 15, a plurality of gas dischargeports 26 a and 26 b, formed in the housing, are adjusted to have two ormore opening diameters and/or opening areas. Therefore, a difference ofthe housing maximum internal pressure can be suppressed at theactivation of each ignition means, and the internal pressure at theactuation of the gas generator is equalized, which provides a gasgenerator for an air bag having a stable combustion performance. Also inthe gas generator according to this embodiment, in the same manner asthe gas generator shown in FIG. 16, the difference of the housingmaximum internal pressure can be suppressed at the activation of eachignition means by making the opening area of each of the gas dischargeports constant and changing the thickness of the sealing means such asthe seal tape 27 to adjust the rupturing pressure. Further, naturally, acontrol of the opening diameter and/or the opening area of the gasdischarge port as well as a control of the thickness of the sealingmeans can be also performed at the same time.

Embodiment 13

In the gas generator for the air bag shown in embodiments 10 to 12mentioned above, it is possible to additionally provide optionalstructures as shown in FIGS. 20 and 21.

<Embodiment with respect to a through hole of combustion chambers>

FIG. 20 shows another embodiment of an opening portion, which is openedby the combustion of the second gas generating agent to communicate thefirst combustion chamber with the second combustion chamber.

That is, FIG. 20a shows an aspect structured such that an openingportion 505, formed on a partition wall 504 (including an inner shell)which defines a first combustion chamber 550 and a second combustionchamber 560, is covered from an outer side, with a suitably formedshutting plate 590 obtained, for example, by forming a belt-like memberinto an annular shape, and thereby a combustion flame of the first gasgenerating agent is not directly contacted. Reference numeral 522denotes a second gas generating agent. FIG. 20b shows an aspectstructured such as to form a notch 512 on a peripheral wall of thepartition wall 504 to form the opening portion 505. Further, FIG. 20cshows an aspect structured such that a thickness of the peripheral wallof the partition wall 504 is made partly thin to form the openingportion 505.

Accordingly, in the gas generator shown in the above embodiments 10 to12, the opening portion, which communicates the first combustion chamberwith the second combustion chamber, may be formed in the aspect shown inFIG. 20 to communicate the first combustion chamber with the secondcombustion chamber.

<Embodiment with respect to structure of positioning an igniter and acable>

Also in the above embodiments 10 to 12, the positioning structurebetween two igniters and the cable, connected to transmit the activatingsignal to each igniter, can be adopted as shown in FIG. 3.

As mentioned above, in the gas generator shown in the above embodiments10 to 12, when the positioning means, which locates the cable 15connected to each igniter as specified, is provided, a gas generator foran air bag, which can securely perform an adjustment of the actuation ofthe gas generator, can be realized.

The lead wire connected to each igniter can be, as shown in FIG. 3,taken out in the same direction on the same plane. Particularly, asshown in this drawing, it is preferable to connect each lead wire viathe connector and arrange the connectors on the same plane in parallel.The connectors preferably draw out each of the lead wires in a directionperpendicular to an axial direction of the housing and also in the samedirection.

<Embodiment with respect to an automatic igniting material (AIM)>

FIG. 21 shows a gas generator for an air bag, in which an automaticigniting material (AIM) 385 ignited due to a combustion heat of thefirst gas generating agent 309 a transmitted from the housing 1 or thelike, is stored in the second combustion chamber. The gas generator,shown in this embodiment, burns, indirectly, the second gas generatingagent 309 b stored in the second combustion chamber 305 b, due to thecombustion of the first gas generating agent, which is left unburntafter the actuation of the gas generator when only the first gasgenerating agent 309 a is burnt. This embodiment will be described withreference to the gas generator for the air bag shown in the aboveembodiment 12.

Also, in the gas generator for the air bag shown in the embodiment 12,the first gas generating agent 309 a and the second gas generating agent309 b are generally ignited and burnt independently by the respectiveactivation of the first igniter 312 a and the second igniter 312 b.Sometimes, only the first igniter is ignited by a current and only thefirst gas generating agent 309 a in the first combustion chamber 305 ais ignited and burnt. Namely, the second gas generating agent 309 b andthe second igniter 312 b are left unburnt. Since such a case causes adisadvantage at the time of later operation, disposal, and the like,after the actuation of the gas generator (only the first igniter 312 a),it is preferable to burn the gas generating agent 309 b in the secondcombustion chamber 305 b at a further delayed timing (for example, 100milliseconds or more) than the normal delayed ignition timing (forexample, 10 to 40 milliseconds) for activating the second igniter 312 b.Accordingly, as shown in FIG. 21, the automatic igniting agent 385ignited and burnt due to the conduction of the combustion heat of thefirst gas generating agent 309 a is arranged in the second combustionchamber 305 b. In this case, the ignition of the second gas generatingagent 309 b by the automatic igniting material 385 is performed at afurther delayed time than the predetermined delayed time (that is, anactivating interval between the igniters) when normally activating thesecond igniter 312 b after the activation of the first igniter 312 a.Namely, it is different from the case of delaying the combustion of thesecond gas generating agent 309 b (i.e. delaying the activation of thesecond igniter 312 b) for the purpose of adjusting the operatingperformance of the gas generator. The second gas generating agent 309 bis not ignited and burnt by the automatic igniting material 385 duringoptionally delaying the operating current to the second igniter 312 b inorder to adjust the operating performance of the gas generator, either.Besides, the automatic igniting material 385 can be arranged incombination with the second igniter.

This embodiment is particularly described on the basis of the gasgenerator shown in the above embodiment 12. However, in the gasgenerator shown in the embodiments 10, 11 and 13, the automatic ignitingmaterial can also be arranged in the second combustion chamber. In thiscase, even when the second gas generating agent is left unburnt afterthe actuation of the gas generator, the second gas generating agent canbe burnt due to the conduction of heat generated by the combustion ofthe first gas generating agent.

Embodiment 14

FIG. 14 shows an embodiment of an air bag apparatus according to thepresent invention in the case of constructing the air bag apparatus insuch a manner as to include a gas generator using the electric ignitiontype ignition means.

The air bag apparatus comprises a gas generator 200, an impact sensor201, a control unit 202, a module case 203, and an air bag 204. In thegas generator 200, the gas generator, described with reference to FIG.1, is used and the actuation performance thereof is adjusted to applysmall an impact as possible to the occupant at the initial stage of theactuation of the gas generator.

The impact sensor 201 comprises, for example, a semiconductor typeacceleration sensor. This semiconductor type acceleration sensor isstructured such that four semiconductor strain gauges are formed on asilicone base plate to be bent when the acceleration is applied, andthese semiconductor strain gauges are bridge-connected. When theacceleration is applied, the beam defects and a strain is produced onthe surface. Due to the strain, a resistance of the semiconductor straingauge is changed, and the structure is made such that the resistancechange can be detected as a voltage signal in proportion to theacceleration.

The control unit 202 is provided with an ignition decision circuit, andthe structure is made such that the signals from the semiconductor typeacceleration sensor is inputted to the ignition decision circuit. Thecontrol unit 202 starts calculation at a time when the impact signalfrom the sensor 201 exceeds a certain value, and when the calculatedresult exceeds a certain value, it outputs an activating signal to theigniter 12 of the gas generator 200.

The module case 203 is formed, for example, of a polyurethane, andincludes a module cover 205. The air bag 204 and the gas generator 200are stored in the module case 203 so as to be constituted as a padmodule. This pad module is generally mounted on a steering wheel 207when being mounted on a driver side of an automobile.

The air bag 204 is formed of a nylon (for example, a nylon 66), apolyester or the like, and structured such that a bag port 206 thereofsurrounds the gas discharge port of the gas generator and is fixed to aflange portion of the gas generator in a folded state.

When the semiconductor type acceleration sensor 201 detects an impact ata time of a collision of an automobile, the signal is transmitted to thecontrol unit 202, and the control unit 202 starts calculation at a timewhen the impact signal from the sensor exceeds a certain value. When thecalculated result exceeds a certain value, it outputs the activatingsignal to the igniter 12 of the gas generator 200. Accordingly, theigniter 12 is activated to ignite the gas generating agent, and the gasgenerating agent burns and generates the gas. The gas is discharged intothe air bag 204, whereby the air bag breaks the module cover 205 toinflate, thereby forming a cushion absorbing an impact between thesteering wheel 207 and the occupant.

Embodiment 15

In FIG. 1, the ignition means comprises two electric ignition typeigniters (12 a, 12 b), which are activated by an activating signaloutputted on the basis of detection by the sensor, and the igniters arefixed to a single initiator collar 13 by fitting in parallel to eachother so as to align in the axial direction, and mounted thereto in astate of exposing head portions thereof.

A method of mounting the igniters 12 a and 12 b using the initiatorcollar 13, mentioned above, is performed as follows. As shown in FIG. 2,at first the igniters 12 a and 12 b are fitted into the initiator collar13 so as to be integrated, thereafter, the initiator collar 13 isinserted into the inner cylindrical member 4 of the gas generator. Atthis time, in order to separate the igniter 12 a from the igniter 12 b,the igniter 12 b is inserted into the separating cylinder 14.Thereafter, by crimping the lower end of the inner cylindrical member 4to fix the initiator collar 13, it is possible to easily and securelyfix two igniters.

Further, when fixing two igniters (12 a, 12 b) in the initiator collar13, a direction of each igniter can be controlled. In FIG. 1, twoigniters are arranged eccentrically with respect to the center axis ofthe housing. In the case of arranging to align the direction of eachigniter (12 a, 12 b), as shown in a back view in FIG. 2, a lead wire 50,which connects the igniters (12 a, 12 b) to a control unit (not shown),can be drawn out in the same direction and on the same plane. In FIG. 2,the lead wire 50 is connected to each igniter (12 a,12 b) via eachconnector 51 a and 51 b and the connector is provided on the same planewhile being arranged in parallel. By connecting these two connectors toform a like L-letter, the lead wire, which transmits an electric signal(an activating signal) to the igniter, can be drawn out in a directionperpendicular to an axial direction of the housing (i.e. the radialdirection of the housing), and the lead wire, connected to each igniter,can be also drawn out in the same direction at that time.

Embodiment 16

FIG. 23 is a vertical cross sectional view of an embodiment of a gasgenerator for an air bag according to the present invention, which isdifferent from the gas generator for an air bag shown in FIG. 1 only ina mounting portion of the igniter.

The ignition means comprises two electric ignition type igniters (12 a,12 b), which are activated by an activating signal outputted on thebasis of detection by the sensor, and the igniters are fixed integrallyin a single initiator collar 13 in parallel as well as aligned to eachother in the axial direction by a resin, and mounted in a state ofexposing head portions thereof.

The structure, in which two igniters 12 a and 12 b are integrally fixedto a single initiator collar 13 by a resin 40 , can be, for example,produced according to the following method. At first, as shown in FIG.24, a single initiator collar 13 having a recess space 13 a in an innerportion is prepared, the igniters 12 a and 12 b are inserted into therecess space 13 a, and thereafter, as shown in FIG. 25, the resin 40 isinserted into the recess space 13 a so as to be hardened.

The initiator collar 13 has a shape and a size corresponding to themounting portion of the housing 3, and the recess space 13 a is at leastlarger than the igniters 12 a and 12 b and does not necessarilycorrespond to the outer shape of the igniters 12 a and 12 b.

The resin 40 is a thermoplastic resin or a thermosetting resin and canemploy a room temperature hardening type or a heat hardening type, and ahardening agent, a hardening promoting agent or the like may be mixedthereto as required.

As mentioned above, by integrally providing two igniters (12 a, 12 b) ina single initiator collar 13, two igniters are fixed to the initiatorcollar 13 to form a single member, therefore, it is easy to assemble tothe gas generator. Particularly, in the gas generator shown in FIG. 23,it is possible to easily and securely fix the igniter by crimping thelower end of the inner cylindrical member 4 after inserting theinitiator collar 13 having two integrated igniters (12 a, 12 b) into theinner cylindrical member 4 to fix the initiator collar 13.

Further, as well as FIGS. 1 and 2, when arranging two igniters (12 a, 12b) in the initiator collar 13, the direction of each igniter can beeasily controlled.

Besides, in the gas generator shown in FIG. 23, the separating cylinder14, arranged between the initiator collar 13 and the partition wall 7,is disposed in such a manner as to provide the hole portion 21corresponding to the outer shape of the separating cylinder 14 on thelower surface of the partition wall 7 or the upper surface (the surfaceof the hardened resin 40) of the initiator collar 13 and fit the upperend or the lower end of the separating cylinder 14 into the respectivehole portions.

The above ignition means is, as described with respect to FIGS. 23, 24and 25, structured such as to include two or more igniters activatedupon an impact, and each igniter (12 a, 12 b) is fixed in a singleinitiator collar 113 by the resin 40. Further, each igniter (12 a, 12b), which is mounted in a single initiator collar 113 and stored in thehousing, is slightly eccentric with respect to the axis of the housing.

In the present embodiment, the ignition means comprises, as describedwith respect to FIGS. 23 to 25, two or more igniters actuated upon animpact, and each igniter (312 a, 312 b) is fixed in a single initiatorcollar 313 by the resin 40. In the embodiment shown in FIG. 26, sincethe igniters are fixed by the resin 40, it is not necessary toparticularly dispose the igniter fixing member. Still, in the gasgenerator shown in this embodiment, the first igniter 312 a and thesecond igniter 312 b are formed in different sizes, and have differentoperating outputs. However, the igniter having the same operating outputmay be used.

Embodiment 17

In the gas generator shown in FIG. 9, two combustion chambers and anignition means accommodating chamber are arranged in the housing 3formed by joining the diffuser shell 1, having the gas discharge port,and the closure shell 2 forming the inner storing space together withthe diffuser shell.

The first combustion chamber 305 a is constituted by the housing 3 andthe substantially cylindrical inner cylindrical member 304 arranged inthe inner portion thereof. Further, the second combustion chamber 305 band the ignition means accommodating chamber 308 are formed respectivelyin the side of the diffuser shell 1 and the side of the closure shell 2by arranging the substantially flat circular partition wall 307 in thestepped notch portion provided inside the inner cylindrical member 304,and further separating the inner portion of the cylinder member 304 intotwo chambers. Accordingly, in this gas generator, the first combustionchamber 305 a and the second combustion chamber 305 b are concentricallyprovided in the housing 3 to be adjacent in the radial direction of thehousing 3.

In the first and second combustion chambers 305 a and 305 b, the gasgenerating agents (309 a, 309 b), which is burnt by the ignition meansactivated upon an impact to generate a combustion gas, is stored, and inthe ignition means accommodating chamber 308, the ignition meansactivated upon an impact is stored.

A through hole 310 is provided in the inner cylindrical member 304,which defines the first combustion chamber 305 a and the secondcombustion chamber 305 b, and this through hole is closed by the sealtape 311. Since this seal tape 311 is ruptured when the gas generatingagent is burnt, both the combustion chambers are communicated with eachother by the through hole 310. The material and the thickness of theseal tape 311 is adjusted to be ruptured only when the gas generatingagent 309 b in the second combustion chamber 305 b burns. In thisembodiment, a stainless seal tape having a thickness of 40 μm is used.The through hole 310 has the opening area greater than that of the gasdischarge port 26, and does not function to control the internalpressure in the combustion chamber 305 b.

The ignition means is structured such that the igniter and the transfercharge are stored in the ignition means accommodating chamber.

The ignition means accommodating chamber 308 is formed by arranging thefirst igniter 312 a and the second igniter 312 b in such a manner as tobe surrounded by the initiator collar 313, the inner cylindrical member304, and the substantially flat circular partition wall 307. Besides,the substantially flat circular partition wall 307 is, as shown in anexploded perspective view shown in FIG. 10, constituted by thesectioning circular member 350, engaged with the stepped notch portion306 of the inner cylindrical member 304, and the seal cup member 360,engaged with the sectioning circular member 350.

Two electric igniting type igniters 312 a and 312 b are provided in asingle initiator collar 313 provided in parallel to each other so as toexpose the head portion thereof. By providing the igniters 312 a and 312b in a single initiator collar 313 in the manner mentioned above, twoigniters are fixed to the initiator collar 313 to form a single member,whereby it is easy to assemble to the gas generator. Particularly, inthe gas generator shown in FIG. 9, by setting the initiator collar 313to a size capable of being inserted into the inner cylindrical member304, two igniters can be easily and securely fixed by crimping the lowerend of the inner cylindrical member 304 after inserting the initiatorcollar 313 having two igniters 312 a and 312 b into the inner cylinder304, so as to fix the initiator collar 313. Further, when arranging twoigniters in the initiator collar 313, the direction of each igniter canbe easily controlled.

The sectioning circular member 350 that constitutes the partition wall307 is formed into a substantially flat circular shape and has anopening portion 351 that inwardly fits the transfer charge accommodatingchamber 361 of the seal cup member 360, a circular hole portion 352formed by cutting out the bottom surface in a circular shape and storesthe upper portion of the igniter 312 b, and a second flame-transferringhole 319, which is pierced through the substantially center of thecircular hole portion 352.

The seal cup member 360 has the cylindrical transfer chargeaccommodating chamber 361 fitted into an opening portion 351 of thesectioning circular member 350 so as to be projected into the secondcombustion chamber 305 b, and the cylindrical igniter receiving port 362formed at a position opposing the circular hole portion 352 of thesectioning circular member 350 and extends in the side opposite to thetransfer charge accommodating chamber 361.

A transfer charge 316 a is stored inside the transfer chargeaccommodating portion 361, and a second igniter 312 b is inwardly fittedto the igniter receiving port 362. The sectioning circular member 350and the seal cup member 360 are engaged with each other by fitting thetransfer charge accommodating portion 361 of the seal cup member 360into the opening portion 351 of the sectioning circular member 350, andan upper portion of the second igniter 312 b, inwardly fitted to theigniter receiving port 362, exposes into the circular hole portion 352of the sectioning circular member 350.

The partition wall 307 constituted by the sectioning circular member 350and the seal cup member 360 are, as shown in FIG. 9, engaged with thestepped notch portion 306 formed on the inner peripheral surface of theinner cylindrical member 304. That is, the peripheral edge of thesectioning circular member 350 is supported by the stepped notch portion306, and the seal cup member 360 is supported in contact with thesectioning circular member 350.

Further, the peripheral edge of the seal cup member 360 is formed bybeing bent in the same direction as that of the igniter receiving port362, and a bent portion 363 is fitted into a groove 364 provided on theinner peripheral surface of the inner cylindrical member 304.Accordingly, the sectioning circular member 350 is supported by the sealcup member 360 and is prevented from moving in the axial direction ofthe housing 3. Further, the partition wall 307 (that is, the seal cupmember 360) and the inner cylindrical member 304 are engaged with eachother without a gap by fitting the bent portion 363 in the peripheraledge of the seal cup member 360 into the groove 364 on the innerperipheral surface of the inner cylindrical member 304.

Accordingly, in the inner cylindrical member 304, the ignition meansaccommodating chamber 308, provided in the side of the closure shell 2,and the second combustion chamber 305 b, provided in the side of thediffuser shell 1, are securely partitioned by an ignition means sealingstructure comprising a combination of the seal cup member 360 and thegroove 364.

The igniter receiving port 362 formed in the above seal cup member 360is structured such that a skirt portion thereof spreads like a fan, andan O-ring 381 is arranged in the inner side thereof, that is, betweenthis and the second igniter 312 b stored in the receiving port 362, inorder to seal between the storing port 362 and the second igniter 312 b.

Further, since the O-ring 381 is also press-contacted to an igniterfixing member 382 which fixes two igniters 312 a and 312 b to the singleinitiator collar 313, the second igniter 312 b is disposed in a spacedefined by the circular hole portion 352 of the sectioning circularmember, the igniter receiving port 362 of the seal cup member, the0-ring 381, and the igniter fixing member 382.

Accordingly, two igniters 312 a and 312 b, arranged in the initiatorcollar 313, are fixed to the igniter fixing member 382 outwardly fittedto the initiator collar 313. By using the above igniter fixing member382, two igniters 312 a and 312 b can be easily assembled to theinitiator collar 313. Besides, in the gas generator shown in thisembodiment, the first igniter 312 a and the second igniter 312 b areformed in different sizes, and have different outputs, and additionally,it is possible to use the igniters having the same output.

The seal tape 320, closing the second flame-transferring hole 319 formedin the circular hole portion 352 of the sectioning circular member 350,is ruptured by the activation of the second igniter 312 b, whereby theinner portion of the defined space in this manner communicates with thesecond combustion chamber 305 b. The first igniter 312 a and the secondigniter 312 b are securely separated by a seal structure comprising theskirt portion of the igniter receiving port 362, the O-ring 381, and theigniter fixing member 382 (hereinafter, referred as “an igniter sealstructure”). Accordingly, the flame generated by activation of oneigniter does not directly flow into the space where the other igniter isstored.

A coolant/filter 22 for purifying and cooling the combustion gasgenerated by the combustion of the gas generating agents (309 a, 309 b)is disposed in the housing 3. An inner peripheral surface of thecoolant/filter 22 in the side of the diffuser shell 1 is covered by ashort pass preventing member 23 so that the combustion gas does not passbetween an end surface of the coolant/filter 22 and the inner portion ofa ceiling portion of the diffuser shell 1. An outer layer 24 forpreventing the coolant/filter 22 from outwardly expanding due to passageof the combustion gas or the like is arranged on the outer side of thecoolant/filter 22. This outer layer 24 is, for example, formed by alayered wire mesh body, and in addition, may be formed by a porouscylindrical member having a plurality of through holes on a peripheralwall surface, or a belt-like restriction layer obtained by forming abelt-like member with a predetermined width into an annular shape. A gap25 is formed on the outer side of the outer layer 24 so that thecombustion gas can pass through the entire portion of the filter 22.

Embodiment 18

When igniters 12 a and 12 b, shown in FIG. 1, are arranged to align inthe same direction, as shown in a back view of the gas generatoraccording to the present embodiment shown in FIG. 2, the lead wires 50 aand 50 b, which connect the igniters 12 a and 12 b to the control unit(not shown), are taken out in the same direction on the same plane. InFIG. 2, the lead wires 50 a and 50 b are connected to the respectiveigniters 12 a and 12 b via the respective connectors 51 a and 51 b, andthe connectors 51 a and 51 b are provided on the same plane in parallel.By forming the connectors 51 a and 51 b in a L-letter shape, the leadwires 50 a and 50 b, which transmit the electric signal (the activatingsignal) to the igniter, can be taken out in a direction perpendicular toan axial direction of the housing (that is, the radial direction of thehousing), (in this case, an angle at which the center lines of the leadwires 50 a and 50 b connected to two igniters 12 a and 12 b cross toeach other is set to 0 degree), and at that time, the lead wires 50 aand 50 b connected to the respective igniters are taken out in the samedirection.

Embodiment 19

In the case of arranging the igniters (12 a, 12 b) as shown in FIG. 8 toalign in the same direction, in the same manner as shown in FIG. 2, thelead wires 50 a and 50 b, which connect the igniters 12 a and 12 b tothe control unit (not shown), are drawn out in the same direction on thesame plane. In FIG. 2, the lead wires 50 a and 50 b are connected to therespective igniters 12 a and 12 b via the respective connectors 51 a and51 b, and the connectors 51 a and 51 b are provided on the same plane inparallel. By forming the connectors 51 a and 51 b in a L-letter shape,the lead wires 50 a and 50 b, which transmit the electric signal (theactivating signal) to the igniter can be drawn out in a directionperpendicular to an axial direction of the housing (i.e. the radialdirection of the housing), and at that time, the lead wires 50 a and 50b connected to the respective igniters can be drawn out in the samedirection.

Embodiment 20

In the igniters 312 a and 312 b shown in FIG. 7, as shown in a back viewof the embodiment 18 in FIG. 2, it is possible to take out the leadwires 50 a and 50 b, which connect the igniter to the control unit (notshown), in the same direction on the same plane. The lead wires 50 a and50 b are connected to the respective igniters via the respectiveconnectors 51 a and 51 b, and the connectors 51 a and 51 b are providedon the same plane in parallel. By forming the connectors 51 a and 51 bin a L-letter shape, the lead wires 50 a and 50 b, which transmit theelectric signal (the activating signal) to the igniter, can be taken outin a direction perpendicular to an axial direction of the housing (i.e.the radial direction of the housing), and at that time, the lead wires50 a and 50 b connected to the respective igniters can be taken out inthe same direction.

Embodiment 21

In FIG. 13, the control unit 202 and the igniter 12 of the gas generator200 are connected by the lead wires, which are taken out in the samedirection on the same plane via the connector connected to the igniter12.

Embodiment 22

An ignition timing of the automatic ignition material, shown in FIG. 12,is determined according to a heat conductivity of a heat transmittingmaterial (for example, the housing) for transmitting a combustion heatof the first gas generating agent, a distance, and the like. In thisembodiment, a non-azide gas generating agent is used as the gasgenerating agent, and the housing and/or the inner cylindrical membercorrespond to the heat transmitting material for transmitting thecombustion heat of the firstly burnt gas generating agent. The automaticigniting material is preferably arranged near each shell in the secondcombustion chamber, and further, is preferably in contact with theshell.

The automatic igniting material can be arranged in the second combustionchamber by means of bonding, inserting only the automatic ignitingmaterial into the independent container to place the container in thesecond combustion chamber, etc. It is preferable to be arranged to becontact with the heat transmitting material.

Accordingly, in the gas generator, in which the automatic ignitingmaterial is arranged in the manner mentioned above, even when only thefirst gas generating agent 309 a is burnt and the second gas generatingagent 309 b arranged in the second combustion chamber 305 b is leftunburnt after the actuation of the gas generator, the second agent canbe indirectly burnt due to the combustion of the first gas generatingagent 309 a, so that it is possible to perform the later operation andthe disposal without trouble after the actuation of the gas generator.

In FIG. 12, reference numeral 23 denotes a short pass preventing member,which prevents the combustion gas from passing between the end surfaceof the coolant/filter and the inner surface of the ceiling portion ofthe diffuser shell.

What is claimed is:
 1. A gas generator for an air bag, comprising: ahousing; an inner cylindrical member provided inside said housing; and asingle collar directly attached to said inner cylindrical member andhaving only a single recessed portion formed in a first side thereof,said single recessed portion accommodating both a first igniter and asecond igniter therein, said first igniter and said second igniter beingintegrally molded with the single collar by providing resin into saidsingle recessed portion.
 2. A gas generator for an air bag, comprising:a housing defining a first combustion chamber; an inner cylindricalmember provided inside said housing and defining a second combustionchamber therein; gas generating means provided in said first combustionchamber and said second combustion chamber; a first igniter for ignitingthe gas generating means provided in said first combustion chamber; asecond igniter for igniting the gas generating means provided in saidsecond combustion chamber; and a single collar directly attached to saidinner cylindrical member and having only a single recessed portionformed in a first side thereof, said single recessed portionaccommodating both said first igniter and said second igniter therein,said first igniter and said second igniter being integrally molded withthe single collar by providing resin into said single recessed portion.3. A gas generator for an air bag according to claim 2, wherein saidfirst igniter ignites the gas generating means provided in said firstcombustion chamber independently from the gas generating means providedin said second combustion chamber.
 4. A gas generator for an air bagaccording to claim 1 or 2, wherein a central axis of said first igniteris parallel to a central axis of said second igniter.
 5. A gas generatorfor an air bag according to claim 4, wherein the central axis of saidfirst igniter and the central axis of the second igniter are parallel toa central axis of said housing.
 6. A gas generator for an air bagaccording to claim 1 or 2, wherein an operating output of said firstigniter is different from an operating output of said second igniter. 7.A gas generator for an air bag according to any one of claim 1 or 2,wherein a shape of said first igniter is different from a shape of saidsecond igniter.
 8. An air bag apparatus, comprising: a gas generatorincluding, a housing, an inner cylindrical member provided inside saidhousing, and a single collar directly attached to said inner cylindricalmember and having only a single recessed portion, said single recessedportion accommodating both a first igniter and a second igniter therein,said first igniter and said second igniter being integrally molded withthe single collar by providing resin into said single recessed portion;an impact sensor for detecting an impact and activating the gasgenerator; an air bag to which a gas generated in the gas generator isintroduced; and a module case for storing the air bag.
 9. A method ofmanufacturing an air bag gas generator, comprising: providing a housing;providing an inner cylinder inside the housing; providing a singlecollar having, at a first side thereof, only a single recessed portion;inserting, from the first side, both a first igniter and a secondigniter into the single recessed portion; providing resin into saidsingle recessed portion; and directly attaching the single collar to theinner cylinder.
 10. The method of claim 9, wherein said step ofproviding a single collar includes the step of, molding said firstigniter and said second igniter such that a central axis of said firstigniter is parallel to a central axis of said second igniter.
 11. Themethod of claim 9, wherein said step of attaching said single collarincludes the step of, attaching said single collar to said housing suchthat a central axis of said housing is parallel to the central axis ofsaid first igniter and the central axis of said second igniter.
 12. Themethod of claim 9, wherein said step of inserting a first igniter and asecond igniter includes the steps of, providing said first igniter andsaid second igniter having a different operating output performance fromone another.
 13. The method of claim 9, wherein said step of inserting afirst igniter and a second igniter includes the steps of, providing saidfirst igniter and said second igniter having a different shape from oneanother.
 14. A gas generator for an air bag, comprising: a housing; anda single collar attached to said housing and having only a singlerecessed portion, formed in a first side thereof, for accommodatingfirst igniter and a second igniter therein, said first igniter and saidsecond igniter being integrally molded with the single collar byproviding resin into said single recessed portion, wherein the singlerecessed portion is provided with a first opening communicating with asecond side of said single collar, opposite to the first side, and forreceiving at least a terminal portion of the first igniter, and a secondopening communicating with the second side and for receiving at least aterminal portion of the second igniter.
 15. A gas generator for an airbag according to claim 14, wherein said single collar has, in the secondside, a first concave portion having a first end face that defines thefirst opening and a second concave portion having a second end face thatdefines the second opening, wherein said first igniter and said secondigniter are molded integrally with said single collar such that theelectrical terminals of said first igniter and the electric terminals ofsaid second igniter are projected from the first end face and the secondend face, respectively.
 16. A gas generator for an air bag according toclaim 15, wherein a first connector and a second connector forconducting electric signal to the electric terminals of said firstigniter and said second igniter are connected to said first igniter andsaid second igniter, respectively, such that the first connector and thesecond connector are inserted into the first concave portion and thesecond concave portion.
 17. A gas generator for an air bag, comprising:a housing including a first combustion chamber and a second combustionchamber therein; gas generating means provided in said first combustionchamber and said second combustion chamber; a first igniter for ignitingthe gas generating means provided in said first combustion chamber; asecond igniter for igniting the gas generating means provided in saidsecond combustion chamber; and a single collar attached to said housingand having only a single recessed portion formed in a first sidethereof, for accommodating said first igniter and said second ignitertherein, said first igniter and said second igniter being integrallymolded with the single collar by providing resin into said singlerecessed portion, wherein the single recessed portion is provided with afirst opening and a second opening respectively communicating with asecond side of said single collar, opposite to the first side, forreceiving at least electric terminals of said first igniter and saidsecond igniter.
 18. A gas generator for and air bag according to claim17, wherein said single collar includes, in said second side, a firstconcave portion having a first end face, and a second concave portionhaving a second end face, said first end face and said second .end facedefining the first opening and the second opening, respectively, andsaid first igniter and said second igniter are molded integrally withsaid single collars such that the electric terminals of said firstigniter and said second igniter are projected from the first end faceand the second end face, respectively.
 19. A gas generator for an airbag according to claim 18, wherein a first connector and a secondconnector for conducing electric signal to the electric terminals suchthat the first connector and the second connectors are inserted into thefirst concave portion and the second concave portion, respectively. 20.A method of manufacturing an air bag gas generator, comprising:providing a housing; providing a single collar having, at a first sidethereof, only a single recessed portion; inserting, from the first side,a first igniter and a second igniter into the single recessed portion;providing resin into said single recessed portion; attaching said singlecollar to said housing; and providing, in the single recessed portion, afirst opening and a second opening respectively in communication with asecond side of the single collar, opposite to the first side, whereinthe step of inserting the first igniter and the second igniter furtherincludes the steps of, inserting the first igniter and the secondigniter such that the first opening and the second opening receiveelectric terminals of the first igniter and the second igniter,respectively.
 21. The method of claim 20, further comprising: providing,in the second side, a first concave portion having a first end face anda second concave portion having a second end face, the first end faceand the second end face defining the first opening and the secondopening, wherein the step of inserting the first igniter and the secondigniter further includes the step of, inserting said first igniter andsaid second igniter such that the electric terminals of said firstigniter and said second igniter are projected from the first end faceand the second end face, respectively.